I agree with @Dan Mackin that COS is a good prospect for long term buy and hold, given the diversity and growth estimates, but I'd suggest Fountain / Security as a starting place for you, not knowing anything beyond the fact that you are serving this great nation (and THANK YOU, sir, for that!). 

John Doe serve in the military and met his wife Mary Doe overseas.

In our discussion he is ready to sell that house and then he tells me he has 25 properties (I had already seen that on the Tax Assessors site) and he said he would like to sell all of the properties.

On 7/16/2018 officers visited the home to serve outstanding warrants on drug trafficking charges on the tenant which turned into officers getting a search warrant of the property.

I actually found the person who served as my 2 year BIC here on BP. 

Should I have them sign a new Month to Month agreement and then serve them the 30 day notice?

just a couple of reasons:No one can buy ALL the deals themselves.Many monetization feeds on a highly ranked site (book sales, pro membership, etc) Trust through notoriety can have a high return on investment (see M.I/oceanpointe for negative example)None of these are good or bad in and of themselves.

DFW is a wonderful area and BP is a great site to get all of your questions answered. 

He has some on his site that he recommends.

I did have bad tenants but you just have to serve them as soon as you can.