I would suggest Daz Studio, as it is free.

If you have a lot of money, Zbrush might be what you want. But as this is a hobby, you probably can't justify $300-400 dollars up front.

Unless you intend to make your own facial and body shapes from scratch, you will probably need to spend around $200 to have a reasonable arsenal of male and female characters, armor, clothing to start doing a whole lot of characters.

The first hundred could get you shaping morphs, the second would be outfits.

Helps?