Will I always be able to get a zero-interest credit card?
No.  There is no guarantee that credit card issuing banks will always use 0% introductory rates to entice anyone. "After looking at the comments, and your replies it seems that your mind is made up: ""You will always be able to obtain 0% credit, and nothing bad will ever happen"". Credit cards that offer 0% on balance transfers are very rare.  Most have a transfer fee of some kind, which acts like an interest rate.  This is a change that probably happened 10 years ago without much fanfare.  From this you can draw a lesson: what changes will come in the future? This site and others a full of ""tales of woe"" where people were playing musical chairs with credit, and when the music stopped, there was no chairs in sight.  Job loss, medical expenses, unexpected taxes, natural disasters can all effect one's ability to make payments on time and happen.  Once payments start being missed or are late, things tend to avalanche from there.  It has happened to me, and loved ones. The pain and suffering is not worth it.  Get out of debt. You claim that you are investing the money instead of paying on the debt, and you are making the delta between your prevailing investment rate 7%.  Did you include the balance transfer fee in your calculations?    First off your investments could lose money.  While 2015 was mostly flat, we have not had a correction in a long time.  Some say we are long overdue.   Secondly, how much money are we really talking about here?  Say there is not a balance transfer fee, you could be guaranteed 7%, and you are floating $10K.  Congratulations in this mythical scenario you just made $700. If $700 changes your life dramatically perhaps it is time for a second job.  This way you can earn that every two weeks (working part time) rather than every year.  Now that will really change your life.  By applying this amount of mental energy to make $700, what opportunities are you missing?   Pay off the debt, you will be much better off in the long run."
Just to put in one more possibility: my credit card can have a positive balance, in which case I earn interest.  If more money is due, it will automatically take that from the connected checking account. If that goes into negative, of course I have to pay interest.  I chose (argued with the bank in order to get) only a small credit allowance. However, I'll be able to access credit allowance + positive balance. That allows me within a day or so to make larger amounts accessible, while the possible immediate damage by credit card fraud is limited at other times.  Actually, the credit card pays more interest than the checkign account. Nevertheless, I don't keep high balance there because the risk of fraud is much higher for the credit card. "I gather from your mention of ""stamp duty"" that you're in Britain?  I'm only familiar with US cards, but for them I can't see that there is any reason (other than a lack of self-discipline) not to use a credit card wherever possible, especially these days. 1) There are plenty of cards with no annual fee. 2) You get anywhere from 1-5% discount/cash back on purchases. 3) Many will give you sign-up bonuses, and a year or more of zero interest.  (So you put that money in your investment account, and odds are you make a profit on it.) 4) Even after the introductory 0% interest period, you get on average about a month of 0% interest between purchase and due date, during which period the money can be earning interest for you. I've made a good many thousands of dollars over the years doing this.  Again, the only drawback I can see is that you may not have the self-discipline to pay off the accounts before they start charging interest." The first thing I assess when looking at new credit cards is whether it has no annual fee, the second thing I look at is how long the interest free period is. I always pay my credit card off in full just before the due date. Any rewards program is a bonus. My main credit card is with CBA, I have a credit limit of $20K and pay no annual fee. I get a bonus point for every $ I spend on it, for which I exchange for store gift cards to help with my everyday spending. Approximately 3500 point would get me a $25 gift card. But my main reward with the card is the interest I save by keeping my own money in a Home Loan Offset account whilst I spend with the Bank's money. Then I pay the full amount off by the due date so I do not pay any interest on the credit card. I only use my credit cards for purchases I would usually make anyway and to pay bills, so my spending would be the same with or without a credit card. I can usually save over $500 each year off my Home Loan interest and get about $350 worth of gift cards each year. If I didn't have any Home Loans then I would keep my money in a high interest depost account so I would be increasing my interest payments each year. Sure you can probably get credit cards with more generous rewards programs, but how much are you paying each year in annual fees, and if you don't have an interest free period and you don't pay off all the amount due each month how much are you paying in interest on the card? This is what you need to way up when looking at rewards programs on offer. Nothing is for free, well almost nothing ! Good credit is calculated (by many lenders) by taking your FICO score which is calculated based upon what is in your credit report.  Building credit generally means building up your FICO score. Your FICO score is impacted my many factors, one small one of which is your utilization ratio of your installment loans like student loans.  This is the ratio of the current balance to your original balance.  To improve your score (slightly) you would want a lower ratio.  I would recommend paying your student loan down to 75% ratio as fast as you can and then you can go back to $50/month. A much better way to improve your FICO score is to have revolving credit.  Your student loans are not revolving, they are installment loans.  Therefore, you should open at least one credit card (assuming you currently have none) right away.  The longer you have had a credit card open, the better your FICO score gets.  Your revolving credit utilization ratio is way more important than your installment loan ratio.  Therefore, to maximize your FICO, try to never have more than 10% utilization on your revolving credit report to the credit bureaus each month.  Only the current month's ratio affects your score at any given moment.  You can ensure you don't go above 10% by paying your balance before the statement cuts each month to get it below 10% way before any payment would be due.  (You should always pay your remaining credit card statement balance in full each month by the due date after the statement cuts to avoid any interest charges.)  Note that there is a slight FICO advantage to having at least one major bank credit card instead of just only credit union credit cards.  Also, never let all your revolving credit report a zero balance in a month, you must always have at least $1 reporting to the credit bureaus on at least one of your open credit cards or your FICO score will take a big negative hit. If you cannot get a normal credit card, go to a credit union and find one that offers secured credit cards, or a bank that does.  A secured credit card is where you place a deposit with the bank that they hold and give you a credit limit to match your security.  Ideally it would be a card that graduates to unsecured after your demonstrate good history with them.  For example, the Navy Federal Credit Union secured card unsecures for many people.  I also believe the Wells Fargo Bank credit card (you can join if there is a family member who served or a roomate who did) also will unsecure.  The reason you want it to unsecure and not be forced to open a new account to get an unsecured account is that you want your average age and oldest age of open revolving credit accounts to be as high as possible as this is another impact on your FICO score. Credit unions that anyone can join include, Digital Federal Credit Union, the Pentagon Federal Credit Union (which offers a secured card that does not graduate), and The State Department Federal Credit Union (also offers secured card that I think does not graduate). One other method to boost your FICO score is to get added as an authorized user on one of your parent's credit cards that has been open a long time.  Not all lenders will report such an authorized user, however, ones that are known to do so are: Bank of America, Citi Bank, and Capital One.  It is a good sign that it will report if they ask for the social security number of the authorized user. However, note that the Authorized User addition can have no impact if the lender is using one of the newer versions of the FICO scoring model, only the older versions reward you for the age of accounts for which you are an authorized user. A very long term boost is to open your first American Express card underwritten directly by Amex such as their Zync card which is pretty easy to get.  The advantage of American express is that they remember the date your first credit card was opened with them and if you open new accounts in the future they will back date the date of their opening to match the date your first card was opened.  If you let your membership lapse, be sure to record the account number and date opened in your personal files so that you can help them locate it again if you reopen as they can have trouble if it has been on the order of ten years or more. Finally, note that the number of accounts opened in the last twelve months is a small negative mark on your score (along with number of inquiries), so if you open a lot of accounts all at once, in addition to bringing down your average age of accounts, you will also get dinged for how many were opened in the last year. It's a good idea to have some emergency money so I would propose a plan that keeps some in your savings:  If the 0% goes away, then consider paying it off, but by that time hopefully you have built up your savings a bit more. Also consider the ability to move the balance from the 2% cards to the 0% one, if that is possible. I can't answer the question if you should or shouldn't get a credit card; after all, you seem to manage fine without one (which is good). I started using credit cards when I lived in the UK as the consumer protection you get from a credit card there tends to be better than from a debit card. I'd also treat it as a debit or charge card, ie pay it off in full every month. That way, because you're not carrying a balance the high interest rate doesn't matter and you avoid the trap of digging yourself deeper into the hole each month. Cashback or other perks offered by a credit card can be worth it, but (a) make sure that they're worth more than the yearly fee and (b) that they're perks you're actually using. For that reason, cashback tends to work best. I'd get a VISA or Mastercard, they seem to be the ones that pretty much everybody accepts. Amex can have better perks but tends to be more expensive and isn't accepted everywhere, especially not outside the US. But in the end, do you really need one if you're managing fine without one? I also had a student loan and glad you are taking a good look on interest rate as it really makes a huge difference. One of the strategies I followed was since my credit improved as I stepped out of school. I took advantage of a good 0 percent credit card. I applied for discover and got a decent credit limit. There are 2 particular things you are looking for in a credit card in this situation  Usually the initial $0 transaction charge is only for a couple of months so ensure you take advantage of that. What is the benefit: Imagine being able to pay off that higher interest rate balance with 0% and not have to worry about it immediately. That way you save on the interest you would be paying and stress as well Watch out for: Although you have to ensure that you do payoff the money you paid through the 0 percent credit card ( which may have been put off for a year or even 15 months or so) other wise you may have to pay it all at once as the offer is expiring. Note: for credit cards ensure to note when the 0% is expiring as that is usually not mentioned on the statement and you may have to call the customer service. I was in a similar situation and was able to pay it all off fairly quickly. I am sure you will as well. One reason why some merchants in the US don't accept Discover is that the fee the store is charged is higher than the average. Generally a portion of transaction fee for the network and the issuing bank goes to the rewards program. In some cases a portion of the interest can also be used to fund these programs. Some cards will give you more points when you carry a balance from one month to the next. Therefore encouraging consumers to have interest charges. This portion of the program will be funded from the interest charges. Profits: Rewards: Some rewards are almost always redeemed: cash once the amount of charges gets above a minimum threshold. Some are almost never redeemed: miles with high requirements and tough blackout periods.  Credit cards that don't understand how their customers will use their cards can run into problems. If they offer a great rewards program that encourages use, but pays too high a percentage of points earned can lead to problems. This is especially true when a great percentage of users pay in full each month. This hurt Citibank in the 1990's. They had a card with no annual fee forever, and a very high percentage never had to pay interest. People flocked to the card, and kept it as an emergency card, because they knew it would never have a annual fee.