I have some good news for you. You said that you're strapped for cash (don't I know the feeling of that.. Well, plastic tubs (such as Rubbermaid and Sterilite) make great housing for these snakes. They're low, with less height to them, and are easier to heat and more secure for the snake to live in. The best part; a tub is much less expensive than a tank, and so easy to clean. I recommend using newspaper as a substrate; it can be completely removed and changed whenever the snake messes it up. A tub is also easy to clean, in that you can completely lift it into the sink easily rather than lugging a big tank around.
An undertank heatpad, on a rheostat dimmer, works great for providing a heat gradient. I would keep the snake in a room that stays around 80 degrees, as is it so much easier to heat the air around the tub, than to have to heat the tub itself to two different temperatures.
I hope that someone with pics of a tub setup will post them. Basically, it's the tub (about long enough for the snake to stretch out diagonally if it wants to.) Then, a substrate, such as several layers of newspaper, or aspen shreddings, or cypress mulch (pine is bad because of its oils.) Then, you'd want 2 identical hide spots, that can be something as simple as 2 identical plastic cereal bowls, flipped over with an entryway cut into them, and a size so the snake can snugly hide inside (they do this most of the time.) One would go over the heat spot, and the other one would go on the cooler side. A water bowl, heavy ceramic works great, would go in the center.
You could apply these principals to a tank if you wanted to, but I would rec. covering the screen lid with plastic wrap mostly to retain humidity. When the snake's eyes start going blue, a shed is coming, and I would jack his humidity up by spraying with a water spray bottle that you can buy at garden stores.
Last but most important, is the lid of the tub (or tank.) I get the tubs (for my snakes that are not in a rack) that latch on both sides, but I still place a heavy brick atop to keep snakes in