My parents, husband and I will be purchasing a property together. Since my husband and I are students, my parents will provide most of the initial downpayment and obtain the mortgage.

After our purchase we'd like to pay them back in monthly installments. For one of these installments, the amount would include half the mortgage payment for that month, half the utility cost for the month and a specific pre-agreed amount towards paying off half the initial downpayment (no interest or anything).

So I'd like to know how much we can give them monthly before it's considered rental income.

Thanks!