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

Are my parents ripping me off with this deal that doesn't allow me to build my equity in my home?
If I understand you situation correctly, then the accepted answer is extremely misleading and incorrect. Your arrangement with your parents is definitely unreasonable. It is definitely not "similar to an interest-only loan". In an interest-only loan, like you can get from a bank, you will loan a sum of money, which you are expected to pay back at a certain time in the future, or when you sell the condo. But you pay back the original sum, not the value of property at selling time. For the access to the money you pay an interest to the bank. The bank gets their profits from the interest. The property only serves as collateral in case you are not able to make your interest payments.  Another way to view it, is that your parent bought (a share of) your condo for investment reasons. In that case, they would expect to get their profits from the increase of the value of the property over time. That looks most like your situation. Granted, that is more risky for them, but that is what they choose to sign up for. But in that case it is not reasonable to charge your for interest as well, because that would mean they would get double profits. So how does the $500 monthly payment fit in? If it is interest, then it would work out to a yearly interest of about 5.2%. Where I live, that would nowadays be extremely high even for an interest-only mortgage from a bank. But I don't live in the USA, so don't know whether that is true there. I think in your situation, the $500 can only be seen as rent. Whether that is reasonable for your situation I cannot judge from here. It should be 75% of a reasonable rent for a condo like that. But in that case, your parents should also stand for 75% of the maintenance costs of the property, which you don't mention, and most of the property taxes and insurance fees. In short, no it is not a reasonable arrangement. You would be better of trying to get a morgage from the bank, and buy out your parents with it.