Offer your thoughts or opinion on the input financial query or topic using your financial background.

Should I fund a move by borrowing or selling other property assets?
When you compare the costs of paying your current mortgage with the rental income from the flat, you're not really comparing like with like. Firstly, the mortgage payments are covering both interest and capital repayments, so some of the 8k is money that is adding to your net worth. Secondly, the value of the flat (130k) is much more than the outstanding mortgage (80k) so if you did sell the flat and pay off the mortgage, you'd have 50k left in cash that could be invested to provide an income. The right way to compare the two options is to look at the different costs in each scenario. Let's assume the bigger house will cost 425k as it makes the figures work out nicely. If you buy the bigger house with a bigger mortgage, you will need to borrow 50k more so will end up with a mortgage of 130k, and you will still have the 8k/year from the flat. Depending on your other income, you might have to pay tax on the 8k/year - e.g. at 40% if you're a higher-rate taxpayer, leaving you with 4.8k/year. If you sell the flat, you'll have no mortgage repayments to make and no income from the flat. You'll be able to exactly buy the new house outright with the 50k left over after you repay the mortgage, on top of your old house. You'd also have to pay some costs to sell the flat that you wouldn't have to with the bigger mortgage, but you'd save on the costs of getting a new mortgage. They probably aren't the same, but let's simplify and assume they are. If anything the costs of selling the flat are likely to be higher than the mortgage costs. Viewed like that, you should look at the actual costs to you of having a 130k mortgage, and how much of that would be interest. Given that you'll be remortgaging, at current mortgage rates, I'd expect interest would only be 2-3%, i.e around 2.5k - 4k, so significantly less than the income from the flat even after tax. The total payment would be more because of capital repayment, but you could easily afford the cashflow difference. You can vary the term of the mortgage to control how much the capital repayment is, and you should easily be able to get a 130k mortgage on a 425k house with a very good deal. So if your figure of 8k rent is accurate (considering void periods, costs of upkeep etc), then I think it easily makes sense to get the bigger house with the bigger mortgage. Given the tax impact (which was pointed out in a comment), a third strategy may be even better: keep the flat, but take out a mortgage on it in exchange for a reduced mortgage on your main house. The reason for doing it that way is that you get some tax relief on the mortgage costs on an investment property as long as the income from that property is higher than the costs, whereas you don't on your primary residence. The tax relief used to just be at the same tax rate you were paying on the rental income, i.e. you could subtract the mortgage costs from the rental income when calculating tax. It's gradually being reduced so it's just basic rate tax relief (20%) even if you pay higher-rate tax, but it still could save you some money. You'd need to look at the different mortgage costs carefully, as "buy-to-let" mortgages often have higher interest rates.