Yes welcome to BPnet this is an amazing forum with plenty of great informers and information. On the home page of this site there is a DIY section with information how to make a tub setup. If its only a year old (about how long is it) you should start with a 32 qt tub which as stated about is very cheap. You should check out www.reptilebasics.com they have stuff called heat tape its very inexpensive and and cheap(compared to other sources of heat) to use and run i think it uses under 10watts of power. The other catch to this type of heat is you need a thermostat but you should have one anyways. They make youre life a whole lot easier by making the temps be exactly where you need them. They have some nice ones on there but you said youre low on money so those won't work. Im not sure where to get one because i have never used them myself (i have a RANCO its on that link i gave you if you can afford get it they are great)but i have heard they are great for a single snake and resonably inexpensive i think under $10. Its called a rheostat it works kind of like a thermostat but completly manual you just keep slightly turning the knobs until you get the proper temps. Anyways if you don't have a lot of money sell that big 75 gallon tank for some money they aren't cheap and you won't be needing it for a ball python the tops you want for a your guy is a 30 gallon. Good luck and keep us posted.