I used to run an independent one-man consultancy advising on technology. Although mostly retired, I still develop hardware, mechanical & software solutions for a few clients, who have specific one-off, or occasional low-volume, technological needs, but for whom the solutions are not core business - such clients generally want a complete package, rarely just a design or a prototype. The only companies I know who sell 'just designs' are at the chip level, e.g, ARM, Magazine articles or scientific journal entries can be a way to get your name known, though they can take a huge chunk of time and effort - a recent (non-electronics) paper a colleague and I published has taken 2y to get past the review stage!

 

Selling electronic designs/systems/ideas is a lot like selling art. It's sold and priced by reputation from what looks like randomly (within the equally qualified) selected 'artists'. Even if you are very good, you need that waiter job until a "breaking through" in the preferred field. You need talent, hard work, networking with possible clients and, a lot of luck.

The 'starving artist/designer'.