Typically 1 gallon tanks are far too small for even flat submersible heaters as the ambient temperature in the location where you keep it should warm it up (or cool it down!).
If you are unable to keep an even temperature, they do make tiny flat heaters for 2.5 to 5 gallon tanks
depends on where you buy it from
Pet stores, like Petco and PetSmart, sell 55 gallon fish tanks. One of these tanks can also be purchased used at yard sales or on eBay. It is risky to buy a used 55 gallon fish tank, though, because it is possible for it to have indiscernible cracks and leaks.
One can buy used fish tanks on AquaBid. On there, you can buy or sell used fish aquariums. Many tanks on there are cheap and afforadable, but make sure you clean it.
No! Think about it. A human can live in a cubicle, or even a shower stall in their own waste, but it sucks and they'll get sick quickly. Get at very least a 1 gallon tank, and preferably as large a tank as you are willing to buy. Heaters are also good; they're tropical fish in nature.
Yes, you can buy pre-made tanks with dividers already in them, or you can buy a 10, or even 20 gallon tank and buy dividers to place in the tank yourself.
Eat Fish and buy heaters
YOu can buy them online at Amazon.com. You can also buy them at local pet stores.
Wall mounted fish tanks can be bought online from many different stores and retailers. Some examples that sell wall mounted fish tanks include Overstock and A Trendy Home.
because the water is to cold
I would suggest that six or eight would be plenty. If you do not have good filtration, reduce this number to five. For six or eight in a ten gal, you should be doing about 30% water changes weekly.
There are 10 gallon aquariums available online from private and commercial sellers. These are small enough to make delivery easy and more affordable than a large tank. For a cheap 10 gallon fish tank I would take a look at eBay or one of the online shops. The link in the resource list will take you to 10 gallon tanks currently selling on eBay.
Lowes, Home Depot and many Sears sell water heaters. You can also get them from plumbing supply shops.