speaking from personal experience, you can pull off a few months homeless in cold-ish temps with the right gear and a little bit of money. if you plan on staying outside, get at least a three season tent (the less mesh walls, the better) with legit rainfly, and 0-degree-rated sleeping bag. I travelled around camping out in cold temps for a while, and if you stay in areas desolate enough where you can build a fire unnoticed, you should be able to get by. when i did this i did have to wake up around 3am every night to feed the fire, but comes with the territory.
before i completely settle down I'm thinking about trying to hop a freight train and ride the rails somewhere. i've read up on it and am aware of the dangers with the RR gangs, homeland security, and the freight car "bulls", but goddamnit I still really want to do it. has anybody ever tried it? been a dream of mine since i was a kid, pee wee's big adventure had a lot to do with it. i realize it's probably a lot harder than the golden days of boxcar hobos with a bindle sack, but i'm sure it can be done.