There of course is no guarantee they'll leave, and then you will have to follow the normal eviction procedure. 

If you paint it all new they’ll not like the color guaranteed.  

Do I roll the dice and hope that they begin to pay and eventually catch up on their $1,200/month rent, or file eviction now which is basically a guarantee that I won’t receive a dime for at least nine months?

Since you are considered "disqualified person" and IRS rules prohibit personal guarantee - you must utilize non-recourse financing.

Unless the contractor is a close friend who is willing to guarantee a certain result for a certain sum or range, I would add 50% to the estimate (so, $45,000). 

The only way you can truly guarantee this is by having the tenant sign an estoppel letter.

@Joe S.Manuel Sepulveda with guarantee plumbing.

@Loree Sarokas notify all people that are on the lease including guarantees.

Something like a personal guarantee, or a promissory note?

The numbers below represent me getting a mortgage for the asking price and I will use 20k cash for the restRent =$1350 section 8 guarantee Monthly Expenses : (I’m leaving out 10% for repairs since things will be brand new) I also leave out 5% vacancy bc I have a good system where when someone’s outs some is in right away1