13 week stays, you wiil be at RV parks and trailer parks, not at cempgrounds. Many have daily rates, weekly rates, and monthly rates. Sometimes monthly and longer rates are quite low because they do not include all utilities.
How much it costs depands on where you are, just as any other rent, tied to land values. I've stayed in parks in the rural south with monthly rates $200 or lower, but you get into resort parks and urban areas don't be surprised by more than $1000 a month. Some of the variation is seasonal. Snowbird winter locations get cheaper in the summer if not also summer resort locations.
Are there parks everywhere? Major metro areas could be a commute, out to where land values are low enough to make trailer parks work. Some cities and counties zone RV and manufactured housing separately, making it harder to find a place for a RV. RV parks exist where land is cheap enough to make them economic and there is enough business to keep them open. I live in an area with moving work populations (agriculture) so the parks are there to accommodate workers around small cities and towns, while recreational users go instead to campgrounds in woods or on rivers and lakes. I've been through other places where all I find are parks and campgrounds for recreational use.
There is also the seasonal thing. RV parks and campgrounds in places with hard winters often close for the winter. There is not enough business, and operating in winter is much more expensive for park owners. Most RVs make poor winter accommodation in any case, not to say it is impossible, because RV and even old trucks and busses get converted to homes in the Arctic: if you can afford to pour the heat into it, any enclosure can be made livable, even tents.
I have not had safety or security problems in RV parks with large long-term or permanently resident populations. People are mostly all ther for the same reason, they have live somewhere to work. They leave each other alone or watch out for each other. Management of these parks typically have tight rules and come down hard and fast on problems.
Go to RVer and traveller reviews of these places, you'll find bad reviews along the lines "full of permanent residents." RVers and people living there to work have different uses for the place, and sometimes get on each others nerve, e.g. one partying at night around the campfire, other getting up a hour before dawn to go to work. You might be in the second group.
You can certainly pull something with your truck big enough for full time living, you and a dog. That doesn't really need to be more than 16-18 feet of TT, though many people like more space and you can probably get to 50%?larger with modern lightweight construction, but I would not think of full timing, especially wintering, in what is billed as "ultralite" or "superlite" as they like to style them.
You can expect to pay as little as $2000 for something old, used, yet usable or might be more than $30,000 for a 20-22 foot TT designed for four-season use (thinking about Bigfoot or Oliver). Durability varies quite a bit, some designs are inneed of more frequent maintenance, others are less prone to shaking apart on the road and damage by weather, but all RVs need regular care, much as does a house. To understand that, you need to have owned houses.
RV parks where you stay long term will have what they call full hookups: water, sewer, electricity. Water and sewer may not be four season, that's the winter operations problem, preventing freeze of hookups. Some RV parks will have cable on a daily rate, while many with longer term residents will let you work out cable and Internet connections with primary providers. But there's a location issue with that, sometimes parks have to be rural to be affordable, and the cable company doesn't go very far out of the city. Similarly, the phone company may not be running DSL out there, unless maybe the RVpark is next to a McDonalds, which will have paid to get the line run to location.
Campgrounds, on the other hand might have no hookups, might have electricty to RV spaces, might have water (or you might have to carry it) may or may not have spaces with sewer connections, but if not will usually have a dump station within a few miles somewhere on therecreational facility. Or it might have full hookups and cable TV, you just don't generally expect that for camping.
If you are planning on a lot of winter work in places that have cold winters, you should have a backup plan. Even if the area has mobile home parks with some RV spaces, there is enough difference in configuration of a mobile home vs a TT that they may not have something that works for you in deep subfreezing weather. Full time RVers usually plan their moves to stay out of severe winter weather.
