Brush up on building code requirements: in basements you're looking for egress windows that are 5.7 sq feet or more openable (3ft by 3ft casement style windows work best), and ceiling heights 6ft 8 inches or greater (as little as 6 ft 4 inches is ok under ductwork and beams though)2.

Brush up on building code requirements: in basements you're looking for egress windows that are 5.7 sq feet or more openable (3ft by 3ft casement style windows work best), and ceiling heights 6ft 8 inches or greater (as little as 6 ft 4 inches is ok under ductwork and beams though)2.

Map the ductwork and mist your ducts with bleach. 

You'd of course have some more into other misc materials (duct work, line sets, registers, etc) but I still think you'd be under $7k total for materials, and yes this is a decent size project but like@John Warrensaid, I'd be shooting for $10-12k total out of pocket from what I know.https://www.alpinehomeair.com/viewproduct.cfm?

The equipment is usually more than the labor for HVAC, especially if your duct work is already in place.

I've researched the AC options a bit and there are 2 that won't require running duct work everywhere.  

Is the space in the lower level conditioned with some sort of ductwork that at least move the air around so that it doesn’t become stale and potential mold source.As others have mentioned look at your gutters and where they drain out.

The performance of an a/c system really depends on how good and correctly sized the duct work is.

That price does not include replacing the furnace or ductwork.

[It is currently empty] Both units have a space for a small stackable washer/dryer BUT there are no dryer ducts/exhausts/vent AND in the upstairs unit the plug would need replaced [it doesn't work and the inspector doesn't know why]I don't plan to buy washer and dryer because of the other expenses we already have [new flooring, plug for downstairs stove, need downstairs appliances] putting us near the top of what we can spend right now, but if I put in the new plug and ductwork, they could potentially buy their own.This is not a high rent area [think 05, 09, 13], but what do you think the positive/negative impact on rents would be to either: a) not repairing plug or adding vent and saying, "Sorry, no washer/dryer" or b) repairing it so they have the option if THEY want to spend the money.I would love to do it just to make my units nicer, but I have to be cognizant of what I'm currently spending.