Well, besides the usual buyer be ware type advice, how much info is the seller willing to tel you as to how he has gotten it ?
Also, being a 93 there would be a Vin number on the date plate, and possibly a matching one on the frame.
If you find one, there is a way you can check by Vin in AZ, to see if it was reported stolen or if the Vin is fake.
If you can do those checks before you buy or somehow take possession of this humvee, your dificulty level on geting a title for it goes way down. ( if you discover that it is reported stolen anywhere, even if you did not buy it, but are just doing your due dillegence beforehand, the nice folks from autotheft taskforce will be asking you where is that humvee now, and how you found it thre. Not a big deal, but can be unplesent to take them back to meet with your seller, if it is that type of a vehicle. If it shows all clear, then ther are several ways to get AZ Title for it. The process is not dificult but requires an inspection, and that a Data plate and a matching secondary plate showing a build date and a matching vin number be precent in that humvee. Price $$ and common cence is your best guide in such a process.
Good luck with it.
ALFA2