Also bear in mind that depending on age and type of construction, the garage may not be able to be permitted as 'living space' due to slab PSI/steel pattern/vapor barrier.

New roof, hvac system, floors, drainage and vapor barriers in the basement, and painted the walls.

It's a vapor barrier and insulation and that room is the warmest in the house.

There were sumppumps and a vapor barrier with gravel ontop installed before I bought it. 

Pictures aren’t clear but think you have a vapor problem under your roof.  

It's not going to matter unless you have some kind of weird vapor barrier preventing moisture movement below the sheathing - water vapor moves through the roof sheathing all the time, and wet wood will dry out the same way (water vapor moving from wood to drier air). 

How well its insulated in the attic and walls, vapor barriers, weather stripping, replacement windows, etc.

On a recent deal, Seller forgot to install vapor barrior.

A smallish starter house where you can add a family room playroom can be a real advantage in a market where a young couple needs the space...make sure you don't skimp on vapor barriers

I would recommend dimpled polyethylene with taped seams and edges on top of the existing slab acting as a vapor barrier.