Raising rents on month to month tenants

[Abraham Anderson]

I'm looking at buying a 30 unit complex. 100% occupied, the current owner has them all month. The rent is anywhere from $50-200 too low when compared to similar apartments nearby.

What's the best approach at raising rents in this situation, while avoiding a mass exodus? Making them sign a lease? Only raising 2-3 tenants rent per month?

A little more background, they are mostly older tenants, & many have been there for 5 to 10 years.