Very interesting and disturbing.

You would disturb the tenant's right to quite enjoyment by renovating the house and then you would essentially change the terms of their lease by adding another roommate to share the kitchen, bathroom, living room, parking, etc.

I missed about 7 weeks of rent on the 2 units (it's a duplex), lost 1 tenant who - because the unit wasn't 100% ready like it was supposed to be - decided not to move forward, and was at risk of losing the other tenant because his move in date kept getting pushed off, had to live without water once he did move in, and dealt with a lot of disturbances all due to this contractor and his negligence to just finish it on time. 

I really hate to disturb the tenants, so you'd need to deposit 10% earnest money up front in order to view the property, and I'll want to compensate my tenants for the inconvenience by paying for them to have a night out on the town, so about $250 of that earnest money will be a non-refundable viewing fee. 

I have left the garage open with everything hanging out for 8 hours when I ran into town for supplies and nothing was disturbed.

If you have someone staying 31+ days, they are going to want a private entrance to come and go as they please without feeling like they're disturbing others and of course, a private bathroom is ideal because most people want their privacy and to keep their own areas clean.

My long term downstairs tenants have had issue with the upstairs tenants yelling and fighting in the middle of the night causing a lot of disturbance to them.

REHAB PROCESS AGREEEMENTTENANT is aware that for 12 month lease time period this RESIDENCE will be undergoing periodic maintenance that may include disturbances to WATER, ELECTRICITY and STRUCTURE.

Every where residents opposed to STR, it has been usually due to fear of unknown, assumptions, rather than real disturbance.

I tend to agree with hunter, rent is being paid already, so you screen her more for damage or disturbance issues with joint income obviously  ok....and you may end up with her there much of the time anyway if they are serious....In my experience, your only risk is the break up and being left with just her, but that may not happen or be a lease or two away and you could cross that bridge then (by not allowing her to be there solo)...