Have you checked the duct work you may have a leak?

@Erin K.no old ductwork?

Anyways I can however give you exact numbers for the contracted items. keep in mind this was only a 750 sq ft house too.Contracted Items:Roof: $4,100Steel high quality Siding from ABC seamless (3 sides only): $6000New paved driveway with retaining wall: $4,400New furnace and some duct work: $4300New gypcrete poured on entire Slab to level floor: $2,300Gutters were included in the siding jobTape, Putty and Patch work on the entire interior: $2000New blown-in insulation and baffles: $1,100My work (materials Only (give or take)):Windows $2500Laminate flooring from Costco: $1200floor Tiles on sale at Lowes: only $50!

Without ductwork I recommend the mini split and as has been stated it's going to cost serious money well over 10k or you can go with ductwork which will be close and then your dealing with more drywall, painting, low lying ceilings, etc.

You say you have electric furnaces, so it sounds like you already have the ductwork.

If you do this set the thermostat yourself and put a lock box over it so the tenants can't turn it up too high or down too low.I also like the idea of closing off the duct work to the upstairs apartment and adding electric baseboard heat, this might cost you a few hundred bucks.

In my area, on a house that would sell for that price, you would find the following costs on the things you rung up:Roof: $6kHVAC (units only, I rarely see ductwork having to be torn out): $3-4kWindows (not sure how many times you are replacing windows): $5k for a small houseFloors: $5kSo let's say $20k for everything you listed.

Basically you mount the fan in the attic and run your insulated flexible ductwork to it and another section of the insulated ductwork up and out through the roof.

Put all new HVAC in and ran new ductwork throughout the entire house.

And did he inspect the ductwork or just do some wiring?