Worn flapper or fill valve in toilet, replacing a faucet cartridge, replacing CH/A filters, change fluorescent ballast, adjust screen doors and windows, flush hot water tank, replace faulty breakers, replace a circulation fan in a refridgerator, replace agitator dogs in a washer, change heating element or ignitor in an electric or gas clothes dryer, lubricating a ceiling fan, replace a p trap under any sink, replace any wind blown shingles, change any thermocouple in a gas appliance, do simple 110v flux core welding, do pvc/copper/pex/galv. plumbing, etc.If you don't know how to do those things yourself, someone else is going to make money off of you.  

You have to supply heat, it has to be set above a certain temperature, In commercial, the landlord is not required to supply heat.

Other thoughts to consider -  it might be good to add a dedicated water heater and heating/cooling system to the ADU - so you aren't fighting with the tenant over the temperature or who is using too much hot water.   

I use an old pair of welding gloves when I trap animals and have to move them.

The kits include compact fluorescent light bulbs of various wattages, LED night lights, smart power strip, whistle that attaches to your HVAC air filter and alerts you when it's time to change the filter, low flow shower heads, dryer vent cleaning brush, water temperature thermometer, refrigerator thermometer, weatherstripping, caulking, foam pipe insulators, window film, rain gauges, etc.

He wants to get a welding machine.

The big day arrived We were able to take out the shearing wall ,remove header and open room The steel structure was purchased by our welder on our crew and he also finished the welding on site.

I suppose if it's electric you could limit the temperature to something more mild.

My buddy had bought a shop for his welding company there in the early 90's and I felt stupid for not following sooner.

My question is can I cut the lower panel or door on the front of the furnace where the intake fan is weld a great in and place for a filter then cut a hole in the closet door for air from my condo to supply intake of furnace thereby eliminating the void that currently draws all the smoke in.