That interesting. Lead paint hadn't crossed my mind.
There's other challenges:
-these sites had generators, so often on site fuel storage. Make sure that's been cleaned up and the tanks (if they are still there) are in good shape. Clean up from leaky fuel tanks gets super expensive. If the tanks are still there, there's three situations:
They have already leaked
-or-
They are getting ready to leak.
-or-
They are currently leaking.
-Asbestos. Needs to be encapsulated/remediated.
-Battery systems. Hopefully they are already gone, if not, that's a huge mess to deal with. Hazardous/toxic material. Heavy as hell and hard to move around.
I've got a couple of tower sites at work, but I don't know what the insurance is like for them. I know we require any contractor, climber, tenant, or other party to have at minimum a $1 million insurance policy to even step on the site.
Towers require periodic maintenance. AT&T was really good about that, but they likely haven't owned that site in a very long time. Inspection would be warranted, and they'll likely find deficiencies. An insurance company may not be willing to supply a policy unless that's been completed.
Adding any new antennas/equipment to the tower itself would need to be reviewed by an engineer. Any time a carrier wants to change out antennas at our sites, we require an engineering study.
Depending on the location/height of the tower, lighting may be required. That requires electricity. There are also some really tight rules about keeping them lit at all times, and the FAA gets really cranky if you don't.
American Tower and Crown Castle own a lot of these sites. If they don't own this one, it's probably because they don't see any potential to make money off the site. Don't buy a tower thinking you'll attract lots of high paying customers. If they are not already on the site, they probably don't want it.
You're a ham, I'm a ham, many of us are hams, so I'm going to call this one: If it's your repeater, then cool, but that's a hell of an investment for one repeater. If you are thinking of offering it to other hams, understand that we are a bunch of cheap SOB's and either won't pay, want it for free, or want it super cheap. Hams are not known for following electrical/building codes, so be cautious about who you let in.
Sharing tower sites between hams and commercial users comes with some challenges. Make sure you understand all those before going down this path.
Cool tower, would be an awesome project. I hope it works out well for you.