You will have to test and prove that the sensor was faulty and not in fact something you did, for example stop under the door for extended period of time.

Or take an extended leave (say 3 months) to test out full time investing and see if you enjoy doing that? 

Just let them know the quicker you rent it you won't be disrupting anymore.I find with tenants like that the likely hood they will actually be moved by move out date is LOW and they will push the limit.. maybe suggest now they extend lease and do an extra month..   

I think the play is to really try to get him out, rather than inheriting him, so I'll just plan to extend the date for as long as they need, and plan my living situation around that.

Not that there’s anything wrong with El Paso just anecdotally, based off my neighborhood, I see a lot of frequent rental property turn over and a lot of for rent signs out for an extended period of time. 

If he is dependant on his brother he has a major life issue problem that can extend into his personality.

The invitation is extended to you as well!

Next time, before you agree to extend a month, insist on a walk-though to determine if the place is in good enough condition to show.

This land would be suitable for mobile homes, RV's, or other housing and city utilities could be extended from my property.Realizing adverse possession is a long term process with risk, fencing, maintenance, taxes, and the associated legal hoops - are there any other "gotcha's" I'm not considering?  

For commercial your build out cost could be lower and your exit motion is similar w/ apartments but again you could have much higher initial vacancies.Financing wise if it's possible start contacting private money, otherwise you can get construction loan, and try to extend to a conventional loan later.