Used 3/4 - 1 ton trucks are easy to come by. Just picked up a nice 2001 for $5k. The last one was $2500 and still runs fine but the rust looks pretty bad (I don't care too much about looks but it was getting bad).
.... was assuming that the OP already had a truck (the $200+ a month was for insurance, maintenance), and could dump it for something more economical for a fraction of the price (it probably is fully depreciated/run its course by now: he may/probably have/has bought it used).
We have visited used campers many times over the past 9 years (in the US and locally here in Quebec) and I've never seen a used hard-side camper that wasn't severely compromised (structurally) under $9000. Not once. Not that it isn't possible to find; however, how much time/gas$ will it cost one to find such an statistical outlier? And even worse: the OP probably can only afford to look locally for camper, limiting his cohort of choice(s) substantially.
I suppose there are campgrounds available to $200 +/- per month out there, but would you really want to chance spending months in such a place (noise, domestic issues, stray bullets, stress, etc...) ? Something in the $400/$500 / month arena could offer him (possibly) reliable neighbors that could watch his 6 (and, his equipment) when he's at work/home.
Lets say his current truck is (used) worth $6000 or so; and spending ~$11,000 on a reliable truck camper big enough to live in = $17,000 (not $20,000; I concede here) :) However, IF he has to spend in the vicinity of $17,000+ to "get into the game", then....
....if the OP has to drive "....every day..." for his daily bread, then sitting a truck camper on the back won't add much to his existing fuel bill. If the OP is forced to drive every day with the hard side camper on board (because of municipal parking regulations, to avoid tickets), then all bets are off. It will be a cost that would be very prohibitive...to say the least.