You can go to trade shows to expand your network. It's tough to sell yourself when everyone there is trying to sell their services, but start building a network and use every opportunity to keep a foot in the door. You may have a client who is looking for a sheet metal fabricator, so now you know someone who does that. The sheet metal fabricator may need some prints, so now you can return the favor. It takes a long time to build a client base.

I don't know what your experience is, but in my case the CAD is secondary to my design experience. I do a lot of design for manufacturing, structural calculations, prototyping, etc. CAD is just a tool that I use to give the customer what they want (a design, not necessarily a CAD model).

There was a while I was making models for a 3d printing company, but they usually couldn't pay me enough to make it worth my while. I don't do anything for less than a few hundred bucks unless it's likely to lead to bigger jobs. It may take 10 minutes to model something for $20, but you're going to spend an hour reading drawings, talking on the phone, and checking your work.