I also say don't get another until you do a ton more research. Buy a few books (I myself have several books on husbandry for ball pythons, corn snakes, and even crested geckos) and read them. Then, take some time fine tuning your set up and get it perfect for your ball python. Once it's perfect and stays perfect, do a little more research! Even I am constantly doing more research and learning knew things. Also, you need to think about the cost involved in getting another ball python. That's twice the food bills, twice the vet costs, twice everything! If you can't afford to upgrade the tank for the snake you have, I can bet you can't afford to care for two ball pythons. Just take things slow and enjoy the one you have. Save up some money and then consider getting another cage for your new ball python.

Ball pythons should not be housed together. While cannibalism is possible, what will more than likely happen is that you will stress out both ball pythons. You could have them both off feed, accidental clutches (or clutches if your female isn't well enough to breed which can be a strain on her body), and you have no way of knowing which ball python left what in the cage. if someone poops, who pooped? If someone regurgitated, who did? If one is sick, they will probably both be sick. Now, cohabbing IS possible but it will take a lot more knowledge and expertise in order to do so correctly. I would not suggest it for beginners. I consider myself a novice and even I would not cohab.

In addition, your new addition will need to be quarantined. That means you need to keep that new addition as possible for a minimum of 3 months (the longer, the better). That way you can look for any signs of illness and fix it before it spreads to your new addition.

As for your heating issues, Firestorm has provided some great links. I would definitely get at least a hydrofarm thermostat (this will help to keep your UTH at a proper temp) and get some acuright thermometers from Walmart (you would need 2 - one for the hot side, one for the cold). That will cost you about $50 or so but it will be one of the best investments you can make for your animals!

I second the question about what substrate you are using and also want to know how thick it is? If your substrate is more than about an inch thick, then your UTH is useless. You need to trim down your substrate so the heat from the UTH can rise to the surface to create your hotspot.