You can start casting for under $100 set up.
You need:
1. A pot. Lyman, RCBS, and Lee offer pots for melting lead. $10 to $12
2. A Dipper. Look at those three again. $5
3. Molds. For the price, you are limited to Lee molds. While not perfect, they generally cast good, usable bullets. You can get them for less than $20 apiece, with handles.
4.Use Lee's liquid alox bullet lube. $3

All you need to add is a heat source, like a campstove, or even your own kitchen stove, if you are careful. You need a piece of broomstick, or dowel, to open the spruecutter on the mold. A cardboard box to catch the sprue and another to catch the bullets.A candle to flux with, and some lead or wheelweights, and you are set.

Granted, the pot on a stove isn't as nice set up as an electric, bottom pour furnace, but it is how I started, and I did fine.
With lee bullet molds, especially the tumble lube designs, you can shoot them as cast, and the liquid alox lube means you don't need a lubrisizer to lube your bullets.