Yeah, I think every region is different and every marina within that region is likely to have its own rules, too. I lived for ten years in a marina in Oregon that was legally permitted (by the county) to have a maximum of four liveaboards. The reason, in our case, was septic tank capacity. The entire marina was on a septic system with a big sand filter and leech lines. I knew of other marinas which were limited by local ordinances, though probably not all.
I recently spent quite a bit of time looking for a slip in San Diego (and finally backed out of a boat purchase because I was unsuccessful.) Down here it seems that anyone can have a liveaboard slip as long as they pay their $400/month. I imagine that is probably due to the fact that San Diego is a good wintering spot and a common preparation/jump-off point for cruisers. It would be bad PR to totally break from that tradition.
Most of the marinas around here charge a deposit for a key card (the ones that don't use PIN pads.) And you can get additional ones for a spouse or a boat partner. I'll admit that I've wondered what would happen if you used one card for the allotted number of nights and then the other one for additional nights. But the marinas I would prefer to be at do allow a sufficient number of days for our use that I doubt I would ever need to try it.
The various marinas all have similar but different liveaboard rules. Maximum non-liveaboard nights might be by week or by month, etc. Likewise, some allow AirBNB while others emphatically forbid it. One even seems to value their AirBNB slipholders above the regulars. I would not want to rent in a marina that allows AirBNB. Too many people coming and going. But if I could have got a slip there, I would have accepted it until I could move.
Apparently unlike in North Carolina, here in San Diego every marina has electronically monitored gates and security cameras. Every one I visited did, anyway. One very nice marina manager told me that they do pay attention to those things. He said it is unfair to charge "all of the pilots and flight attendants" liveaboard fees when they aren't there every night and let others spends lots of nights on their boats without paying the fees. (Interesting that pilots and flight attendants are such a big part of their liveaboard clientele, but not surprising once you think about it a bit.)
And as I saw during my hours spent in many marina offices looking for a slip the staff do know the liveaboards and most of the regulars quite well. At one marina a guy came in and the manager and he conversed for quite some time, while I waited. They seemed to be co-workers talking about this or that problem or project going on in the marina. After the guy left, the said "sorry, he owns that boat" and pointed out the window at a yacht in the 60' range that had to cost in the millions. I suddenly felt overdressed in my clean tee shirt, cargo shorts, and Birks.
At another marina I'd been looking at a boat and then visited the office when I was done. After I told them I'd been looking at a boat for sale the first thing they asked was who let me in. And then they checked their computer to confirm it. I was a little put out at first, then I realized that I might really appreciate that attention to detail if my boat were moored there. But don't try to stay more than your allotted nights there.
I did get the impression from almost all of the marina managers that I talked to, that a "good tenant" gets a lot more leeway in most matters than a "bad tenant". But that's kind of a catch-22 since a "good tenant" is probably the one that rarely needs the leeway. They all emphasized that a well-kept boat owned by a quiet couple who pays their bills and doesn't pollute the water is their ideal tenant. A couple of marinas looked at the boat we were buying and our credit score and subtly suggested that we might have suddenly moved to the top of their waiting list. But unfortunately, that wait was still likely to be many months long.
