Well 3d cad can be a bit expensive and can also take some effort and time to learn. 17 years ago when I first bought a 3d cad program, we went with VX, now ZW3D, because of the cost, the usability, and the fact that there were lots of tutorials for it, and you didn't have to go to a school to learn it. They were based originally in Florida, but sold to the Chinese, which may be a problem for some, however, the development was kept here in the states. Here is a link for a reseller with some pricing. I think that you can still download a trial version that will work for a month, if I am not mistaken,
The Case for Inexpensive CAD/CAM
And another link for a lite version
ZW3D Lite|Easy 3D CAD software|ZW3D Lite price-
Have not used this one so cannot speak for it.
Anyway, the full blown version is very powerful, works well, has an integrated cam package if you want, and will model about anything you would want to do. I have done very large assemblies with many layers of sub assemblies, and have had few problems. And modeled a number of parts that I have made for guys on this form
Just my $.02 about an affordable package.