Your Thingiverse only has two over year old designs? How serious are you?
Yea, I am net positive with my 3d printing, that includes buying another printer. You have to remember that the raw material the 3d printers use is relatively cheap. I can print off something that costs me less than $1 per part, not including labor, electricity, etc, and still charge multiple times what it cost me to make. #d printing is basically a money making machine if you find the right niche and are decent at design.
So what I sell is kind of a replacement part for a machine that usually wealthy people own. Sorry I know that's super vague. But anyways I redesigned as one part to make it custom and now I sell those custom parts. The website I use to sell them very specific to people who own these so if I had any advice I'd say get into a niche market.