You are going to have to buy an inverter for the power. It needs to be converted from Alternating Current (AC) to Direct Current (DC).
By the time you spend the money on that you might as well have gone with a sub/box/amp combo. If money is a problem, search craigslist. People are offing stuff like crazy to pay bills. Sad, but true.
Honestly, I wouldn't even mess with it. When you cheap out, you end up doing it all over again in the future and it costs you twice as much as it would have; had you done it right in the first place.