Getting creative with down payment?

[Justin Reid]

My idea is to get the seller to make my 15-20% down payment.

In my area small single families sell for around $50k. My idea was to offer slightly above ask, say $52k with the seller giving me back 15% or $7800 for my down payment netting them $44,200 for the property. 

Basically I want to leverage the seller and not use any of my own cash. As long as the house appraises there should not be any issues correct? Has anyone successfully done this? Am I missing something? I feel like I would have heard about more people doing this if it was feasible. Just trying to think out side the box a bit.