At that point the locks need to be changed and all existing tenants given new keys.

However, you would be committing mortgage fraud if you represent that you will occupy and then you do not.

However, if you're looking at an existing franchise that owns the land and building, or if you are looking to buy a new franchise and want to place it on land or in a building that you own then that would be a great 1031 opportunity. 

I'd rather go with a wholesaler or local pre-foreclosure before committing to something on zillow that seems like a grab for an eager newbie investor...

Don't commit to them just let them know your testing waters and are about to jump in this beautiful game.

.$8.00 for a combo set...way cheaper than home depot and better than spending my time trying to rekey an existing lockset...

I think it would show your integrity and commitment. 

If you have a longer lease, you'll be committed to dealing with that situation unless you can get them to agree to move out sooner.In our leases for the extra room(s) in the house, we made sure to spell out everything such as what was common space and what wasn't.

Instead, put as much towards your next property purchase and don't look to maximize expenses on existing properties. 

But also agreeing with @Wayne Brooks this sounds like a wrap around deal otherwise the existing lender could exercise the due on sale clause, another thing to look into. that's my .02