check lease and local regulaton.

In some states, landlord can not terminate lease and ask tenant move out if the owner not go to use it for his/her own primary home use.

You may give 30 day notice to raise rent. The tenant must give you 30 day notice. Or after notice to pay you 30 day more rent.

And if they already buy a home, you do not worry not able to collect rent as they have asset.

Raise rent also may subject local regulation.