Besides the fact that large enclosures can be stress on ball pythons.....you will definately have to consider the fact that an enclosure of that size is going to be hard to heat properly, so make sure you buy all your heating supplies, set them up, and get them running at the right temps and humidity before purchasing the bp.....it is better to be very prepared then risk stressing out your snake or causing it to get sick because the heating is still being 'worked on'.

I also seem to notice that you keep mentioning 'cheap'.....keeping a reptile correctly is not always the cheapest thing, so be prepared to spend a few bucks.

Good luck! and lets see some pics when you are done