Buying a property in AZ with no leases, is it a bad idea?

[Shel D.]

In the process of buying a 4-plex in Phoenix, AZ. Fully occupied but no lease in place. The seller did send me some old expired not signed leases. These leases do not hold if challenged in court. I am no lawyer but this makes me nervous. What if the tenants decide not to vacate, the rents are much lower than the market rate- what is our recourse? We are not getting a steal on this property, Phoenix being an amazing real estate market we did not expect it anyway. Please help!