You can use a camp stove, or small fire, and a cast iron pot, or anything that won't melt at the temps you need to melt the lead.
I have both steel and aluminum moulds. The aluminum ( Lee ) moulds are cheaper, and come with handles, and they are great moulds. About $25.00 for them. The steel ones, will run that and more for just the mould, and then you have to pay about that for the handles. Your choice. I really like the Lee moulds. When I first bought my TC Hawken kit, and finally got it finished, and sighted it in at a friends house, it was just getting dark when I got the consistant shots I was looking for, and it was just about dark by then. So I only had one Maxie ball left. And I was heading out to a place to hunt very early the next morning, so I just grabbed my little lead pot, that used to be electric, but burnt out, and some roofing/plumbers flashing, and headed for the area to hunt, and got my camp set up, and hit the rack. Got up just before daylight, made some hot tea, and melted some lead, and poured my self six Maxie balls, just as the sun was coming up. Didn't get a shot at a Deer, saw plenty, just weren't in muzzle loader range. I try to keep it at a maximum of a hundred yds. It shoots dead on at that range, and I don't like to push my luck. With the .50, and pure soft lead, it will do a lot damage. A friend of mine shot one in the same area, at about 75 yds or so, and it just fell over, never kicked, or moved.
No you don't need an electric melting pot, but they are handy. Again lee makes a nice one fairly cheap.
Do like Brian said, and look around for a roofing company, and tell them what you need. Check some old dumps also. If you can get the wheel weights, get them, but save them for use with modern bullets, for your pistol, or low loads for your rifle. I used hard cast bullets for my .44 mag, and .44 special, they shoot very well. Good luck in your search, and try to stick to soft lead.
Wayne