So my answer is .... it depends on what you want to do, just be sure you understand what all is involved in hanging your own shingle on the door.

Sounds like you have a retail contractor.I can get a 4 unit building that is almost 5,000 sq ft completed with hardy and labor and materials for 8,000.On the roofs you have to pay attention to number of layers put on it and also hail damage,bad run routes for water drainage and flashing and caulk issues.Here is Georgia you can have a 20 year roof but because of our weather extremes the expanding and contracting will wear out the roof shingles much faster.

Or are they run down, paint and shingles peeling off them, with iron bars over the windows and broken down cars parked on the dead lawn?

The kitchen has only bare walls (no appliances, cabinets, countertops), certain sections of the roof have been patched with felt paper instead of shingles (most likely the whole needs to be replaced), basement has limestone walls and is moist (I believe that water is leaking into it).

Appliances, cook top on outdoor kitchen, and kids using the pool and ripping shingles off to play Frisbee. 

Paint doesn't last much more than 5 years unless it's on cedar shingles then it may last longer, Behr is good paint. 

My shingles were installed that afternoon. 

You could 20 year shingles up there and you could be on your 15 year and they could last another 15 years with a little patching.

When you compare costs for a used 16x80 and add in the cost of locating it, moving it, rehabbing it, the used home often ends up costing more than a new one assuming you are looking for a late model vinyl and shingle home.The types of deals that existed in the early 2000s were a one-time phenomena that may not happen again anytime soon.

Just an update though - during home inspection we found settlement cracks located above garage door, several cupped shingles on the roof and some soil eroding near side grading.