At least in every marina I've dealt with, if you wanted a slip, which is what it sounds like the OP has, you are REQUIRED TO HAVE INSURANCE. Usually, it is a minimum of $100,000 liability coverage.
If a boat and and RV are both being used for strictly shelter, then the boat is going to have higher maintenance, since the underwater gear still needs to be maintained to a certain degree—through-hulls, plumbing, etc, are still equipment that needs maintenance, even if the boat is not being used for transportation, since if they're not maintained, the boat WILL SINK. The plumbing on an RV can be ignored, and there will be no risk of the RV sinking.
Sorry it took so long to get back to the forum, but not being some keyboard commodore I was out actually sailing this weekend, I did have a chance to read all your posts though.
First let me say I can only speak from my own experience, I have had my boat in 3 different marinas over the last 15 years, 2 private and 1 run by the state. I've never been asked to show proof of insurance. Hard to believe they would want $100000 liability coverage just to park the boat, maybe they've seen you sail before... just kidding.
In regards to thru hulls I must admit I've been remissed, in the 15 years I've sailed mine hard I've never had the occassion to bother with them other than to repair the knot meter and to disconnect the cockpit drain to install a backing plate and new grundgon for my rudder. Maybe you could enlighten me as to the extensive maintenance the plastic thru hulls you find on most production boats need. Other than replacing a $3 hose clamp now and again what would make it so cost prohibitive?
As for the head if you're in a marina use their facilities. If anchoring out get a portapottie from West Marine for $100. The only servicing that needs is to be emptied overboard t night when on one is around.
Boats only need the basic CG required safety equipment to be legal. Motor vehicles need to pass a yearly safety inspection whether you park it in one spot all year or commute 150 mile to work each day. That means all lights, mirrors, brakes, suspension, glass, exhaust, and in NY you have to also pass an emissions control test, anyone have to replace an oxygen sensor lately?
As for RV's anyone I've ever been on has a propane gas system for heating cooking and usually even the fridge. IF YOU DON'T MAINTAIN YOU PROPANE SUPPLY SYSTEM YOU WIL BLOW UP!!!
Oh sorry my cap lock and bold type buttons must have been stuck. I must apoligise, I wouldn't want anyone to think I was some kind of duffas that thinks typing in bold capital letters makes his point more valid.
But as a practical matter you can live in a camper cheaply, however the places that would allow you to squat fro free are likely to be inhabited by a lot of transents, drug addicts, crazy people and the rest of societys dregs. Myself I would feel safer leaving my possessions in a boat in a bay with 30 other derilect boats than in a camper with 30 groups of homeless living under blue tarps.
Hey but what do I know I even have a splice in my anchor line.