Traveling, or something permanently parked in the Bay area?
Continuously traveling, a motorized RV can make sense. Permanently located somewhere, or staying in any place a long time, a towable RV usually works better. If not moving around, manufactured housing is usually more space for the money, and often lower cost rent, compared to RVs and RV parks.
You'll need to figure out how much space you really need, to determine the size of the RV. RV floor space ranges from less than 80 square feet, up to about 400 square feet. Manufactured permanent housing starts at just over 400, can go to at least twice that size. These are definitions, because when a RV/housing manufacturer crosses that 400 square foot threshold, the construction standards change.
Life at the kind of RV park that lets people stay six months or longer is usually not that different from life at a permanent living trailer park, and the quality of life, the services provided, the kind of people you have as neighbors, will often depend on how high the rent. Rent, in turn, will depend on location and land values, with the cheapest RV or trailer lots renting for about half the rent of the least expensive apartments or small houses in the same neighborhood. You won't find RV parks in particularly nice neighborhoods, but you will find them at recreational destinations, and those can be much more expensive than permanent housing (but still less than hotels at the same place).
Most of my experience has been in the middle of the country, staying at the kinds of parks used by people who are there for seasonal work or temporary work. Most of the time these people are neighborly, helpful when help is needed, and look after each other. It is a bit like small town life, even though you don't have the long-term relationships that hold small towns together.
I've paid rents ranging from $300 to $1200 a month. At the lower end that usually includes a power and water hookup, but no sewer connection (there will usually be a dump station on the property), and if it is a public park there will often be a limit on length of stay. It gets a lot more expensive when the park is close to an urban area, it can go a lot higher than the highest I will pay, so I don't spend much time RVing in or near major cities.
There is a class of urban dwellers who pay no rent at all, living in cars or vans, parking on the streets. This can be harder to do if it is seen as a problem in the area, and is more difficult using something that clearly looks like a RV. I'm thinking that this is not what you are thinking, but if it is, I might be able to find some references to this lifestyle.
