Hell, I would. I know what you mean by being a poor teenager, I am too. Luckily I had a few 10 gallon tanks laying around that held water, and got a free good one at a yard sale. As for heaters I had to buy them with gift money.
I use a Hydor mini heater for Horizon's small 2 gallon round kitter keeper and it seems to work just fine. She's active and still a pig when it come to food ><. However I will tell you that they are only designed to heat up the water about 5*f more then room temp. So if you have a really cold room, you may want to surf craigslist and find a cheap tank and heater (They do pop up, I've seen them, some people even give some filters and decor away with them) And if you wish to house more Bettas, a 10 gallon tank can comfortable house up to 3 males separated by homemade dividers made from those cheap report folder bindings and some plastic canvas mesh. Together can cost as much as 5-8 bucks depending were you buy them. and the tank on craigslist can be as low as 15 bucks with a heater. But make sure you have a thermometer so you can have an accurate temperature for your bettas. even with a hydor mini heater. I would get a thermometer just to see how much warmer it makes the water, if it's too cold, start investing in a tank and heater.
Another idea that was brought up recently was using clear storage totes as a tank. It's a great idea. However some clear totes aren't CLEAR, they're translucent and has a frosted look when looking in from the side. However, they are cheap, and you can get them in huge sizes. I'm even thinking of getting a nice big one for Hassan my baby Snapping turtle as he's getting a wee bit big for his 10 gallon tank.