She's not suppose to even be there.Do I have to formally evict her?

I would skip the formality by going to State Real Estate Board compliance filing.

He is officially a long term renter and I would have him do a formal lease (which really means nothing), and submit to a background check. 

@Tom Gimer Thanks Tom...in this case there are two many issues that me as the seller and my future buyer just don't understand....especially with owner financing and lead paint disclosures etc , etc.....but I will put as much in the offer as I can but it will still have wording in the offer that it is contingent on our lawyers  creating a formal sales contract in "x" amount of days....I know of no other way to do this since I lack the knowledge to cover all the bases.....but I will take your advice and get as much in there up front ...if there is a better way then please let me know

Your really doing this for formality sake. 

A judicial foreclosure in which they must take you to court and sue you into foreclosure.

There is no formal registration process for either an ESA or a service animal. 

I was formally with erentpayments.com and we all know how that fiasco went down.

Based on those contingencies and a formal offer letter that is accepted, I almost have a deal done.

Upon taking possession I made him aware i was going to need him to leave, and then a week later, gave him formal notice in writing (and notarized) that he had 46 days to leave.