Well, you can get a prepaid cell for about $30 a month or I think $.50 a minute if that's helpful to yah.. also you can get a yagi off ebay for about $70-100 (assuming you have some place to pick it up) in addition wep networks can be cracked easily (cracked many myself) if that doesn't sting your moral code

(a yagi extends wireless usable signal I would say half a mile)
These are best tips I have for mobile living.. maybe you could consider a vehicle if you could raise yourself up some gas money..
I once had a idea and this requires a car

but you can pick up things of the craigslist: free list and sell these things locally or via ebay and make a living that way