Just curious if this is doable/practical for a single person w/no kids?
Yes, absolutely.
This woman lives in a 97 Jetta while she works and attends college. Parks mostly in shops, and tried for a long time to legally and openly live in the parking lot on-campus.
These folks tried for a while, failed (equipment) and are doing it again:
This guy was featured on AOL or yahoo
This couple are my inspiration. They were my first exposure to the concept of living without a home and b&m job. I had never ever considered the possibility.
http://cheaprvliving.com/howtoconvertavan.html
(CRL has a forum too)
Yahoo has a group called Vandwellers:
http://autos.groups.yahoo.com/group/VanDwellers/
Really what it comes down to: What are your reasons for vandwelling?
Short term or Long term?
Must you live in the city?
Do you plan to continue a full time job while you vandwell?
How handy are you with general and auto repair?
First choice is going to be the vehicle. If you want the bees knees - get a Roadtrek from the mid-late 90's. They have 17, 19, an 21 foot long models. The 19 is most popular, while the 17 looks just like any other van out there. You'll get a toilet, 3 beds, cooktop, inverter, and A/C, and a 150AH or so aux battery. These are sometimes outfitted with a genset too (But I think thats the 21 footer, not sure). They run about $10k for these models, and is pretty much the top I would be willing to pay for one.
Anything that looks like an RV is going to be a problem in an "urban" environment. Cities often have codes that seek to prevent this sort of thing (they think of it as vagrancy). But it all depends on your environment.
I grew up in SE Mich (Ann Arbor/Ypsi/Redford) - I would seriously consider doing this there. They don't have nearly the homeless problem as where I live now, so at most you'd keep getting the "4am knocks" on your van where they have you show your ID and make sure you aren't dead/actively raping someone. However down where I live now - in South FL - there is no friggin way. People would be calling the cops nonstop on you, stealing your tires, busting windows, etc.
In any event, do NOT expect the air to work anywhere you aren't on shorepower, or running the generator. It won't. Solar isn't enough for A/C, you need something like 6 4D batteries and 6 250W panels to be able to do it - it would cost over $10k and might not do it.
The biggest problems people face isn't really how to make enough money to live. There are enough odd jobs (work camping, ebay, part time gigs, barback/waitress, freelance IT work) to make your insurance and food money, even enough to cover renting an RV spot on a monthly basis. The biggest problems you'll face - where to park "legally", the stigma of living in a van, and equipment failure.
You can get a shitty class C, but these are more trouble than they are worth. You cannot park in the street and expect to get by in any city environment for longer than a couple days. Class C's are NOT meant to live in full-time, and even the new ones have disclaimers in the warranty. They are "cheap" and tend to fall apart. Not that a Class B is any better, its just that the frame is still originally the vehicle that was built, while the Class C is heavily modified. Forget about a Class A - you won't make any money back - these run from 100k-250k.
Another possibility is of course to modify your own van. Ideally you take a phone company/carpet guy/contractor rape van shell (windows you can have or not) - add tanks, build shelving/cover floor, add convertible seats. The big advantage of a class B is that the tanks are often under the floor/under the chassis like a fuel tank, while you could do that, damn you gotta be a good welder LOL. So you probably can't make it as nice as a fully appointe class b, but you can definitely have a decent 5-10 gallon shower, full size toilet, 20 gallon water tank, microwave/stove/generator/aux battery/lighting/tv/internet/telephone, etc.
Oh yeah and the hitekhomeless folks run
http://www.freecampsites.net a site which crowdsources free overnight parking - mostly in national land/state parks/easy to stealth parking lots, and low cost campgrounds.
Contrary to popular belief, not all Walmarts allow overnighters.