We used an ozone generator to eliminate smells.  

I have tried to fight this battle on the West coast and you can for sure landlock a property if  the person owned both properties and failed to give a together with easement when they sold one .the easement by necessity sounds like the play here and then its up to a trier of fact and maybe the other party wont want to spend legal fee's defending. ???

Has anyone charged a smokers deposit so if the apartment then does smell like smoke can use to help rectify.  

You don't have any proof that she has moved another person in, and just because you smelled them smoking doesn't mean that would hold up in court.

My real estate agent in the area went by and took some video and described it as "creepy and old," the tenants had smoked so the smell was awful, and the neighborhood was "hood" - she didn't really feel safe there just taking a look. 

I think there's a way for both of you to come out smelling like roses.  

But I have not noticed any moldy smells or seen any signs.

Should I walk away from the deal or fight the uphill battle of managing the roaches.

Its a losing battle and a reality that the sellers of these MHPs with POHs will have to face.

@Rick Robles I would agree with @Austin Petrie in a sense that buying a deal right is half the battle.