That depends on the type of furnace and AC conditioner $5500-$7500 for Basic
equipment only” Additional features are going to cost more.

15 to 20 years but it could be more with proper maintenance.

For routine maintenance. I run the unit then clean the unit and run it again. Make sure everything is running properly. Flame and parts are working optimally. Look to see if anything is out of place or leaking. Look for parts that are worn or need replacing.

Standard residential is 1 to 5 tons and anything over is commercial.

45000 to 150000 BTUs for furnaces and anything greater is commercial.

Once we have the sq footage and the layout of the house, I would
need to provide an estimate. New equipment estimates are free.

I recommend everyone keep the thermostat set to the on position. That way the blower is on all the time and the air will circulate around the house. Equipment is made to run.