Current Owner Can't Produce Leases

[Jason V.]

I'm currently negotiating on a triplex that has had the same owner since it was built in 1989. Additionally, One of the current tenants was the first tenant in the building, and one of the other tenants has been there for 17 years. 

I made my offer contingent on receiving the current leases/contracts as well as the P&L for 2015, but the owner is saying he doesn't have that information, but "He's told the tenants the property is being sold, and they will have to work with the new owner" which is nice, except as far as I know in New York, if one of them pulls a rental agreement out of their back pocket saying they can live there for the next 5 years at current (under market) rents, I have to honor that. 

How should I handle this situation? At current rents (it is 100% occupied) and the price we've agreed on the CoC is solid, but I would really like to get rents bumped up to market rates (one is at least $100/month low.)