If they see stains on the trusses inside the attic there is a leak.

My primary concerns would be the electrical issue and evidence of dampness and/or staining in some of the areas. 

Stains, sagging paint, exposed anything indicates the roof has a problem.

I hear the past owner used to take care of the property, until he got hooked on drugs.There were a few areas noted on some of the ceilings of water staining and dry wall sag...mainly in the first floor units.

The iron destroys everything, washing clothes, toilets, faucets, everything gets stained or eaten through.

We are going to sand the ceilings and refinish the floor so that all of the interior wood has a more natural look to it, and then apply clear coat to the flat surfaces, and a darker hickory stain to the trim. 

While you are up there, make sure it's copper wire not aluminum, knob & tube is okay if it has been maintained, but if you see rat chewings on wires or holes in the ceiling looking into the sky or stains on the wood, have those checked out.

Cash invested: $1,000 I spent my savings on a paint sprayer and grew my knowledge on different paints and stains for fences, as well as application methods.

Something else to note; even old stain and varnish can have lead in it.

Exterior Decking:Exterior Decking damaged unsafe to use with advanced wood decayExterior Window and Door Framing:Active moisture staining rot and termite damagestone foundation:significant pargement and mortar deterioration needs stone repointing and parged to avoid potential stone shiftingEnvironmental concerns:Basement lot of mold Mold TestsConfirmed cladpsporium and hyphase and pencillium type of modls in basement at unusual levelPest TestsVisible evidence of wood destroying insects and dea insects and termite related damage noticed.