I gave them a 90 day notice that I was going to sell the house and they would need to vacate after 90 days.

**"Cash for keys" is a strategy that landlords can use to encourage a tenant to vacate a property without having to go through a formal eviction process.

The second thing I will say is that you as the buyer have to do your due diligence throughout the whole buying process, even to go to the property and make sure a tenant is vacated prior to closing the deal.. 

You can search your local area to establish comps through visiting various short term vacations sites (Verbo and Airbnb).  

I have found a tenant that has agreed to a relatively unconventional agreement for my furnished property in a popular vacation location.

Augusta, GA is the home of the Masters and a lot of folk vacate their residences in order to make some cashola.I don't mean to bust your chops on this as the info was great, but it isn't a loophole and the IRS doesn't consider it a loophole.

The tenant has caused damage and broken the lease so she is going to vacate in December.

Often, safer to file with the understanding those fees may be wasted, but better than waiting and then the tenant does NOT vacate (causing more lost time/rent).Usually court date will be 2-3 weeks after filing, which means 1st or 2nd week of following month.

Flips, BRRRRs, vacation rentals, etc..

I mean, they are technically a squatter themselves so why not just put another squatter in that will make them miserable wow keeping them from damaging the property who will then vacate the property whenever that one’s gone.