Briansue, I haven't been to Cancun parks. In Baja people don't get TIP on RV when going in. Aduana doesn't ask, gringos don't volunteer to pay.
$6000 a year is a lot of money for a shack on a campsite. Though Playa del Carmen is a too good location, nice beach and 50 miles from international airport, basically a Cancun suburb. From what I see, homes in Baja are generally more expensive than in mainland Mexico. Too many expats in Baja. Oddly, RV parks in Baja are not too expensive, I don't think there is anything over 4000. Some places start from $700-800, if you're OK without running water and are willing to install the underground cable from the power pole at the camp entrance.
The laws in Cancun are same as anywhere East of Sonora - you must have TIP. When TIP expires, you lose few hundred bucks deposit. You won't be allowed any more TIPs in future, but Cancun is cheap to fly in. So what are we left with - the possibility of govt coming after your RV with a tow truck? Pure loss for them, old trailer has little value. I also wonder if RV parked on a private land is immune to this kind of enforcement - as long as you don't tow it on public roads.