There are a lot of modeling applications out there. Some are free, some are inexpensive, and some cost more than a used car (and some cost more than a new car).

For free, Blender , is one of the best programs out there, but for many it's interface is a PITA. However, they just released a new version.

Wings3d is nice. Some people swear by Truespace. And all three of the above are free.

Peguses is a simple modeling program that is designed to model Poser/DAZ models and is under $100. I'm not sure that it gives you anything more than Wings.

I call anything below $1,000 inexpensive, just to have a price point. I really like Modo as a modeling program, but it lacks character animation.

There is also Z-Brush, but that is a very different sort of modeling/sculpting application and is nice in it's own way.

Other modeling programs are Shade and Hexagon.

Most of the others that you hear of, like the Autodesk products (Maya and 3ds Studio) cost over $3,000 so I haven't even tried them.

I would suggest that you start with a simple and free modeling application and learn with that. Then if you find you like it, you can better decide how much money you want to invest in 3d modeling. Trust me, you can spend quite a bit without realizing it.

My recomendation would be to start with Blender because it is free and it has a lot of tutorials easily available. I wish that I had done so before spending money on other programs because I'm coming full circle back to Blender.

You can find more information about modeling applications on the forums of Renderosity and DAZ.

Good luck and have fun!