BTW, pretty if she stays an extra day she'd only owe for one day - no court is going to rule for you on that, and you'll look like a jerk of a donkey's hind end for trying.

What @Steve Vaughan and his wife did is perfectly normal and actually streamlines things a little to shave some costs of extra work.

Plus when you move out the extra unit gets rented.

I want to do this all while ensuring my tenants' housing needs are sufficiently met.I'm considering starting with a 5% management fee (and no extra fees), giving the first 3 months of services free as a sort of trial period, and allowing owners to back-out of my services with only a 30-day notice and no extra fees.

It's a hands on learning experience where they can also earn some extra cash.

Charged extra (nickel and dimed for everything else).

(summer months)  We listed our home on airbnb to make extra income while away...without a permit and when we returned after 2 months away...we found we had 2500 dollars worth of fines waiting for us. 

If your average heating bill is $150, you may not collect enough in the winter months when the bill reaches $225 but you'll collect extra in the summer when it drops to $65.

More importantly they’ll keep you on the right side of fair housing and they may even pay for themselves by charging more rent than you would or not asking so much it stays empty for an extra month. 

If you don’t have a dedt service rate issue than you could get the extra money and just hold it in cash or invest it and us that money to pay down the extra.