You can get a digital thermometer with humidity disply witha long corded probe at walmart for about $15.
Hides can be plastic bowls, with holes melted(cut if you smooth the edges) in the "bottom"/"top" or in one side. Or you can use clay pots, and chip out a entrance, or chip out the drain hole larger for a entrance. As long as they are the same, it doens't matter.
The decorations(wood/plastic plants) can be gotten at the Dollar Tree type stores, just wash them well before using.

You technically can use newspaper for substrate, plastic bowls upturned for hides, and replace it later if you wanted it to look better.
You can't really skimp on the UTH, the thermostats(rheostats), etc. Those are what would hurt the snake if they fail.
I see tons of the tanks with lids on craigslist or at yard sales, myself. I've bought some before, when I needed one quick. Petsmart is a decent price normally.
Good luck.