I'm confused--I thought I'd read about you already having a 5 or a 10 gallon tank that you'd divided.. that didn't end up working out?
Personally, I'm not a fan of getting the cheapest thing out there. After all, you are making an investment in the next 5-7 years of this fish's life when you get a new fish tank. Starting cheap only means you waste money when you get tired of doing constant water changes and decide to finally upgrade. The best advice I can give you is to just be patient. Wait until you have the money to afford the setup that works with your life and promotes the well-being of the fish--don't just jump on a dinky piece of junk because it's cheap.
Personally, I prefer the 3 and 5 gallon marineland eclipse tanks--they're not the cheapest out there, but they're well-designed and they're a quality product. Often you can find these and similar models on craigslist for only a few dollars, so that would really be your best option. Try to order any other supplies you might need online--it will help you save a lot of money even including shipping. I do all my online shopping here: http://www.fosterandsmithaquatics.com/
It's great for buying gravel, silk plants, decorations, filters, heaters, thermometers, test kits, dechlorinator and other items that get marked up enormously by the pet store. They offer reasonable flat rate shipping and they take paypal, so you don't need a credit card to order.
Another good option if you happen to be in Canada is this site: http://www.bigalsonline.com/