For instance, I had to have an AC coil pulled and cleaned and the drain pan replaced.  

I'm about to purchase another property with the electrical wiring missing (removed for the copper) and the coil inside AC handler missing (stolen). 

Maybe it's a great situation to tap off your existing split-system (if you have a forced air system), depending on existing furnace btu capacity and condensing coil tonnage.

This is for a 1,200 SF ranch with 500 SF finished basement.New 2.5 ton AC unit & coil - $2750 Replumb entire house (1.75 baths) - supplies, wastes, & vents (excl. fixtures) - $5300Rewire entire house & garage to code - new panel, service ok (excl. fixtures) - $5300Paint interior 3 colors (walls, ceilings, trim), incl. removing some wall paper, most surfaces required 3 coats, incl. paint utility basement walls & floor - $4650I'm in a medium-sized midwestern city with average material & labor prices.

However, I am not sure how well these details would work when applied to $30,000 houses.As for the things you always hear about - AC units, furnaces, coils and water heaters.  

There is a spring like coil tool you can buy if it becomes a repetitive issue.3) If they request the floor strip to be fixed, then just knock it out on your visit.

Hey JordanReduce your cost dramatically your in Texas so your mostly non-union hire some guys to do the tear off you can get that done for around 600 bucks buy 16 squares of asphalt shingling  have it delivered, hire a guy with an air compressor and nailer offer him 35 bucks a square he'll be done in less than 3 hrs.

I have put about 6 roofs on with a masterforce roofing nailer with not a single problem.

So I would probably have someone take a look at the units to be sure they are charged properly, filters are clean, coils are not dust-covered, etc. 

You could also install hardwood, but that requires a special flooring nailer - which could be rented - and an air compressor.In the bathroom, you could remove linoleum or outdated tile and replace with tile.