I am working with an elderly owner to purchase the home he lives in and a short-term rental house he owns across the street.  He is mandating I give him 6 months to find and purchase a new home. He is elderly and has unique requirements for a new home (needs to be one level, a garage, etc).  If he doesn't find a home within 6 months, he said he doesn't have to sell to me.    

I would like to purchase the properties but don't want to wait around for six months, bypassing other properties I could purchase, interest rates rising, etc. all for him not to find a home he likes.

He could come back in six months and say he couldn't find a home or if the market continues to increase back out of the deal because he "couldn't find a home."  

Any creative ideas on how to make this work where he would have some skin in the game and I could ensure he is diligently trying to purchase a home?

Thanks in advance!