Do you want good or cheap? What all do you plan to do with it? If it's just simple 3D modeling, then just about any 3D will do. If you are going to do complex surfaces, etc, you will have a lot less headaches if you buy a higher level program. I use SolidWorks everyday for work. Easy to use. If you have to buy it yourself it, or any others, it will be pricey ($3-4000). If you can find someone with a work liscence or a student version, it will be free. You will need to look at the horspower required by the program to run on your computer. It's mostly the graphics card that will be lacking. I'm not a computer guru, but it seems like most of the good graphics cards for 3D modeling are the same ones that are used for gaming. The more complex the parts you are going to make, the more hp you need in your computer. The rendering of simple to moderate complexity parts will put an "average" computer on it's knees.
Hope this helps
Later
Chris