I would also investigate the possibility of filing a mechanic’s lien on their property.

Each month the Rent Board selects a random sample of 10% of all notices which state owner or relative occupancy as the reason for eviction, and transmitts this list to the District Attorney for possible investigation.

The snippets of the lease you mentioned are quite short and not enough to see if it will cover you to do the full investigation on the buyer of the business.  

You can use any legal investigative tool you like, that isn't really the issue, it's what you base a denial on. 

If owner, then here is your decision tree:Buy with sub2, and then hold and rent, sell as a lease option, or sell on terms to someone else (you could also list it if you wanted to, but I doubt you'd have success when the owner didn't unless the agent is at fault).If collect one time assignment fee, then here is your decision tree:Put property under contract to buy (with this, you can put the property under contract as sub2 and assign sub2 deal to someone, or assignable contract for deed, or assignable lease option).If you have the option to go either way, and you're local to the area, then there are more advantages to buying with sub2 (or being on the deed via a mortgage wrap, because then you have equitable title and you're not assigning - no one can ever start an unlicensed broker investigation on you if you're on title).So which exit strategy sounds best to you?

An investigation was done and the boyfriend was receiving mail in his name to the property.That was enough evidence to prove the terms of the lease were being violated.

@Patrick Madigan I would investigate the "why's" and "how much $ to fix" of the 14 vacant units?

I'm investigating purchasing a unit, and my main experience is here in Las Vegas.  

@Jay Hinrichs - Well, definitely something to investigate so you can share your real estate knowledge with the world... or at least a few new Green Egg recipes.

Skip tracing is using a database usually accessed by a private investigator to find some ones location.