I have a little 2D Autodesk experience from years ago (and I can relearn quick)....but I'd like to do some 3D cad work to have a friend with a CNC make me some stuff. He'll make whatever I want as long as I give him a cad file of it.

What are my choices? And is there anything affordable out there?

Been using smartcad and autocad for 20 years. I bet you could find an old version for a little bit of nothing if you check out the computer shows and such. Want be any support or upgrades but it ought to get done what you need.

I use a $100 MasterCam package to design all of my parts. Works just fine and most machine shops can handle native MasterCam files. If not, just export a DXF or other format.

Andy, where did you get MasterCAM for $100? I have an educational version of it, but it doesn't have the Post routines to generate the G-codes. I can do tool paths with it and everything, but it's useless without the post for my mill.

I bought it from the local MasterCAM dealer. I just have Design. I don't need to generate tool paths myself anymore and it didn't sound like the OP needed that capability either. If you have a CNC mill then you need the much more expensive version of the software but most people do not have CNC milling machines in their home shops.

Please remember that A CAD doesn't do any analysis or engineering, other than telling you the material is perforated ("cannot perform this operation"): GIGO.
If you're sure what it must look like (an adapter) you're fine.
If you're making a rod or rocker arm (complex 3-dimensional structural shape) from billet, you need to copy a know-to-be-successful design very closely, or an FEA program.

this is opensource and takes a little bit of linux knowledge to get off the ground but it's free..

http://www.caelinux.com/CMS/

I have a good friend who's a mechanical engineer that has had some success with it.

Thanks for all the input....basically I want to do stuff like simple adapters, reluctors, etc.

I'll look into all that....

I think it's called Alibre, that has a free, feature limited version.

Err, guess it's $100, https://www.alibre.com/products/hobby/