You didn't mention the mechanical set up, so I am not sure hat utilities the tenants are paying, but this deal sounds way over valued by the owner.

The current state of the roof and mechanicals will determine if you replace them once or twice over the life of the home.

There may be UNRECORDED liens, like welfare department, nursing home or mechanics leins, you would be responsible for all of those also.8. 

you'd want to stud it out and insulate and drywall so there is room for mechanicals and the insulation is key.On the outside you could cover it with 3/4" plywood, tyvek and the Hardi or Vinyl .  

You can take your car to a certified mechanic and pay for their expertise and guarantee that your car will be fixed properly.

A debt is not secured by your home if it is secured solely because of a lien on your general assets or if it is a security interest that attaches to the property without your consent (such as a mechanic's lien or judgment lien).

Even a sump pump can fail; they are electro-mechanical devices, so mechanical failure of electricity outage can both bring about failures there.

Carpet and paint only, some mechanicals replaced, gut jobs where the copper and electrical needs to be put in etc.??

Can pull permits, not including mechanical (unless he's licensed in that field). 2.

The problem comes when a rehab just is cosmetic while leaving all the mechanicals/structural deficient.