Let me summarize what I hear to make sure I got it correctly:- STR has higher property management rates (25-30%) unlike 10-12% for LTR- Local policies are more dynamic for STR and what is allowed now, can be banned in the future (I saw that happening in HI when considering buying a real-estate there), should have a backup plan- STR require more management time thus if managed personally, should expect more involvement- Look at Florida and Carolina (NC?)

Usually you can quit claim deed the property without the lender even being involved.

Do I need to get the sheriff involved, or can I proceed with turning off the utilities effective that date? 

She is saying to contact him to see why he hasn't been working on it and if I can get my money back but she doesn't want to be involved.

I am a local agent in the DFW community and love to see when people are getting involved in real estate!

Honestly, it looks like your investor is not going to be involved with the deal. 

Is it possible to get the police involved without the eviction process, and tell them I have my leasee who agreed to move out but yet someone else who is not on the lease is in our property?

It's going to be a more stressful and involved process than buying an existing property, but you will learn a ton! 

Either let them go through with the Assignment or do the double close, but you can't be involved in both.So you might want to contact the closing attorney and make sure everyone is on the same page as it sounds like there might be a miscommunication there.  

I haven't been involved with that myself however so my knowledge is limited.