Buying multifamily but the owner wants to stay for 2 years.

[An Duong]

Looking to buy a 7 unit multifamily in Rhode Island but the owner wants to stay in his unit for two years at a reduced (less than fair market) rate.  I am not sure how much hardball I should play with this.  The deal is good enough that I would'nt mind having him stay for maybe 1 year but 2 years seems like too much.  He is 72 years old and says he needs that time to move him self out. Any advice would be helpful.

Thanks!