Important to distinguish the two as one heats a liquid to use for hot water/heat while the other produces electricity, so they're about as different as a steam engine and an electric motor.

With out a seasoned HVAC-R tech checking the windings of the compressor, and fan motor, I would never trust a used unit, not to mention the possibility of the coil having a leak, which you won’t even be able to test, until after the purchase.

Now it cools to 68.Another from a fixer I just bought needed a fan motor on the 12 year old AC.

@Louie Jhan Centeno Maglaque  Can you do simple repairs like replace a garbage disposer, replace a hot water heater, replace a motor or capacitor in a central air unit? 

I've used it for everything between roof repairs, A/C blower motor replacement, washer leaks, and general house cleaning/deep cleaning.

I tried using the capacitors on my air compressor motor but they didn't do the job as they were both a little different in size.I have gotten pretty good about troubleshooting the basics on heat pumps since I have over 20 of these things.

Ductwork can be cleaned and sanitized no need to replace.. the coil can be cleaned or replaced and that’s all that’s to that the blower motor in your furnace blow air across your cold coil that’s how you get cold air.

It runs great no issues this season I changed the furnace blower motor for $500/-

If it's possible to run the vent down, you might be able to put one of those in the bathroom wall, fairly high up, and then run the vent down through the wall, into the crawl space, and through the side of the house.You can also get "remote" bath fans, which work kind of like a central air conditioner - you install a small vent grille in the bathroom, put the motor and blower above the ceiling or under the floor, and run ductwork from the grille to the motor and from the motor to the outside.

And then some other things to protect it long term and alleviate some capex things (gutters, basic updates to electrical, a few plumbing repairs, a little motor work in the garage and basement, a new concrete front stoop).