Found out a person not on the lease is living in my rental

[Jason Hines]

I’m a new landlord. I just purchased my first duplex in October and I live in one unit. The tenants in the other unit have been here for 8 years. The seller raved about how great they are and I have had nothing but good experiences with them so far. They keep their unit clean, are not loud, took care of snow removal during the storm last week.

Their lease ends on 1/31/21 and we have already signed a year extension for just the two tenants starting on 2/1/21. I just found out that a 3rd person is living there.

What should I do? I think we need to amend the lease and add the 3rd person. Should I also be raising the rent? The only utility that I pay for that would be affected is water. But we haven’t got a water bill yet to get a baseline.

Any and all advice would be greatly appreciated!