Tenant's 30 year old son moved in, do I increase rent?

[Tom Lipps]

Hi BP Community,

I've been looking for a rental property for about a year now in Cincinnati, Ohio and am about to close on my first property (Duplex, 2bdr, 1bdr)!

I'm inheriting two tenants on the first floor (the 2-bedroom). Their lease expires in Sept 2018 (ouch) and they're paying well below the market price rents. I found out today that their 30 year old son is going through a divorce and has been living with them for a few months with his dog. The 2 tenants already had 1 dog, their son has brought in another.

To account for this 3rd adult and 2nd dog (not on the lease) I believe I should do the following:

 1. Have son complete an application (including background check). Do you agree?

 2. Raise rent, but by how much? They currently pay $600/mo (market rate is about $696).  Maybe I use the son and dog as a reason to at least get them in line with the market? Thoughts?

 3. Lease doesn't specify anything about pets... Do I have the right to increase rents to account for the additional dog?

 Thanks for any advice!

- Tom

PS: The lease does stateonly the two people listed on the lease may live on the premises.