On the AC guy, you got lucky! I typically don't let tenants work on the house, but if he was a certified or professional I might allow it.
Let me give an example of why.
Tenant moved out, let's call her "Jane".
I inspect the house....the garage door opener doesn't work at all....it was only about 4 years old. I did some basic tests and could not find out what was wrong....so I called professional. The guy checked it and said "What the heck...have you been messing with this?" I told him all I did was test for voltage at the unit. He said "Someone has switched the wires on the circuit board on the controller and fried the entire board."
So when I billed the tenant Jane, she confessed. She said that the opener stopped working and her "boyfriend" said he could fix it since he knew a lot about garage doors. He obviously didn't. She said they are no longer dating lol. She was billed $295 for a new opener.
Tenants THINK they know how to fix things, but they usually don't. Like most of us here, I have many stories of tenants who tried to fix something and made it worse. The most recent was ....
I was installing a furnace filter at a unit. I went into the bathroom to wash my hands when I was done, and I noticed duct tape on the shower head where it screws on to the shower arm (the small angled pipe that comes out of the wall). I asked why it was like that and he said "It was leaking, so I fixed it".
As it turns out, he had simply channeled the water so that it ran behind the wall unit and down into the wall cavity. There was water damage on the drywall behind the shower wall. I had to remove the front shower wall, replace the drywall, and reset that section of shower wall...billed them $265.
I just tell my tenants to call us when something's not right. I give them a few stories during lease signing such as the above where tenants try to fix things and it ends up costing them MORE...sort of trying to scare them out of attempting repairs themselves.
I hope you have better luck. --99.92.xxx.xxx