No utilities on, no items in the unit etc. then you generally have a right to secure and release.Here in GA an attorney will usually say if it appears abandoned and no more than 500 of value or less is present then go ahead and re-key etc.

Find a good locksmith who will do a master system for you. 

We will ask the plumbers, electricians, appliance repairman, locksmiths, painters, landscapers, floor covering installers, etc. what works best and why.

Locksmith at their expense.

Put in your lease that if they lock themselves out, they have to call a locksmith if you aren't available. 

I am less stringent about some of my trades people when the house is vacant and under rehab.When I do the key box, I temporarily rekey the lock to a generic key that will only work on one door.  

And if there's truly an emergency without you being home, they can just break a window.If he insists, say sure, give him a key, then have it re-keyed again. 

Maybe I'll get lucky and they will move out on their own before I show up with the sheriff, a locksmith and a moving truck. 

yes, you hold title, have a locksmith come out, present the documents that you own the house and take pictures and or video of the place on the day you do it noting it was vacated by previous occupants.

I lined up a locksmith, my agent, and will have a sheriff present to make sure the appraiser gets in without a problem.