I rented it to 2 roommates and the lease is up at the end of July. 

The rules are a little different if the adult occupants are unrelated (roommates).

Roommates? 

They're oddly kind of like having a roommate, where if they were in a large apartment complex, they wouldn't have the same type of relationship - it would be more anonymous.Why were they both needing a garbage can? 

I found a duplex that I could use an FHA loan and then live in one 2bed unit with a roommate and rent out the other unit.

If you buy a 3br/2ba and get two roommates, you'll have a desirable house and probably be living for free.

This is often a sticky situation when one tenant in a roommate situation wants to leave and the others have to agree on the new roommate.While the departing tenant would remain responsible for the lease until a suitable replacement is found, the other roommates need to understand that the landlord expects the FULL rent to be paid. 

During the process I also bought my second investment property which I have rehabbed and moved into with roommates for the time being. 

She either gets the ability, which is essentially more pay from another job, or she finds an acceptable roommate.

What I would do is offer to allow her a room mate but the rent will go up the full $400.