Creative Financing For Colleague Seller Home Purchase.

Suggestions?

Have a colleague who’s relocating. He knows I have a rental and came to me with an off market opportunity to buy his 1 year old town home. Good location. Market value, maybe just slightly under it since we aren’t using realtor. 

He has to leave to start new job. Wife is staying back until January. they either want to sell then, or sell now, and she’ll rent it from me during interim. 

They’re open to creative financing. They don’t have a ton of equity. Maybe 40k or so.  I don’t have enough capitol for a traditional 20-25% down on a traditional lending option.  I can do a portion of that and was thinking of amatorizing the rest to them over an agreed upon rate. 

Any ideas how anyone would structure this?