He says if I pay him full asking, he would provide me with the 20% down payment since we could avoid realtor fees, and make up the rest by paying full asking (he had it appraised), rather than accepting an offer under asking.

I've been in real estate since 2015 and currently offer accounting services to investors.

There's nothing better than getting an FHA or conventional offer accepted by an unsuspecting seller, knowing you will have plenty of opportunity to re negotiate once the appraisal comes back.

Seller is an idiot for even accepting your offer.

Your parents decide they need their cash back for medical reasons.

Happy to offer up some more insights if you're interested.

Admittedly I am new to this and I haven't written a creative offer before. 

Focus on how to juice cash flow if possible (rent by the room, separating spaces, etc.) or decreasing expenses (assuming a loan, looking at new build incentives, aggressive offers w/ rate buy downs that work for you, etc.) 

Turnkeys offer less hands-on management which is ideal for beginners and it give you valuable experience as a landlord.

He is a mentor of mine as well, and is not so interested in making money but rather he told me that he likes to see 7% in his passively invested accounts, so I offered and he accepted that I would pay him 8% APY On the principal that I borrowed.