My dad took out a HELOC on his home and gave me the money to build my home. But I make the monthly payments to his HELOC. Would this be considered rent or mortgage paymen

[ToddL · Accepted solution]

As far as you are concerned, the monthly payments to his HELOC lender aren't rent or mortgage payments.  

Technically, your dad lent (or gave) you the money. By making the payments on his HELOC you are, in manner of speaking, paying it back to him with interest. 

He is the only one who would be able to claim the mortgage interest deduction; to deduct mortgage interest, a mortgage loan has to be legally secured by your (in this case Dad's) residence and he has to be responsible for payments. 

It isn't rent, unless your dad owns your house. Rent isn't deductible to you, but would be income to him.