It depends on the selling price, but if we can assume the property will be sold at a profit, they are getting a pretty sweet deal at your expense. They are both getting about 5.2% interest on their money, plus the lion's share of any property appreciation.

I would say that fair would be either of:

1. They pay 75% of interest, taxes, condo fees (you're the only one benefitting from the utilities, so that's all yours to bear) and they get 75% of the gross sale, or
2. They pass through to you the interest cost of money they provided (5% does sound reasonable), but on sale they only get their original principal (115k) back, or
3. They operate it like a real mortgage where you pay them interest plus a portion of the principal each month and on sale, they only get the balance of that principal back (less than the original 115k).

It depends on the selling price, but if we can assume the property will be sold at a profit, they are getting a pretty sweet deal at your expense. They are both getting about 5.2% interest on their money, plus the lion's share of any property appreciation.

I would say that fair would be either of:

1. They pay 75% of the taxes and condo fees (you're the only one benefitting from the utilities, so that's all yours to bear) and they get 75% of the gross sale, or
2. They pass through to you the interest cost of money they provided (assuming they had to borrow it, and 5% does sound reasonable), but on sale they only get their original principal (115k) back, or
3. They operate it like a real mortgage where you pay them interest plus a portion of the principal each month and on sale, they only get the balance of that principal back (less than the original 115k).