Existing Tenants - Raising rents and leases

[Thomas Ebenhoch]

I am in the process of buying a triplex that I plan to owner occupy. The house has 2 units rented with the third vacant.

The house is being sold by a family trust and I was told by the selling agent that the tenants have lived in the property for 15+ years. I was also told that the tenants do not have lease agreements in place, they have a verbal month-to-month agreement with the previous owners. 

The current rents are also very low, 600 for a 3BR and 375 for a 2BR. Market rents for my area are in the 900-950 (3BR) and 700-800 (2Br). I am planning on raising the rents to be comparable to other properties in the area.

Has anyone experienced an issue like this before?