Walmart has a 10gallon aquarium with hood and light for 20$ and an extra 15 bucks for a aqua-tech fifteen gallon filter, all in all it should run about 34 dollars, a air pump is a good idea to, I'm on a super tight budget, I Just watch DIY videos on YouTube and make what I need with what I have, hope I helped!
Very good points.
Another very good option is to look on craigslist. Resale value on aquarium parts and equipment is usually somewhere in the neighborhood of 10-50% of retail cost.