4 Plex Evaluation Question

[Ace McCarty]

I am still new to real-estate investing and I am currently evaluating a 4-plex and was hoping I could get some general feedback. 

The 4-plex that is for sale currently has tenants in every unit on a Month - Month Lease. The 4-plex passes the 1% rule and depending on the rent that is charged looks to have a cash flow that I am comfortable with. 

From keeping the tenants what are my options if I were to purchase this place? Am I able to have the tenants sign a new lease once the ownership of the building is transferred? I would prefer a 1 year lease for the stability of income. 

I know the current landlord pays all utilities, and depending on the rent that is charged that is something I would prefer to change going forward, I am guessing I will risk losing the current tenants if I change anything to their lease if they decide to stay? 

Is there anything else I should know or ask the seller of this place? Is interviewing the tenants something that is recommended?