It's mostly one guy in the Salt Lake City area who enjoys the challenge and uses his video channel to convince a few others to do the same. He's a real expert in animal handling whose obsession with hunting and willfulness (no one could convince him that minks were impossible to tame) seem to help him relate to mustelids. But minks' stubborn and feisty temperaments make them some of the most difficult animals of their size for most people to keep as pets. I follow this community pretty closely.
500 Euros seems like a steep charge. I've never heard of a startup that charged you. Usually it's the other way around - they pay you, even a small amount. Most startups are also unable to raise money. This startup would need to differentiate itself from the competitor and/or show traction to be able to raise money, unless they're VERY well connected with the angel investors.
No, I don't think you are the wrong type of person for a developer role. You're obviously engaged in building things, and your portfolio of work can speak volumes. You could always show off your work and mention that it's profitable, and some interviewers might forgive your lack of experience when they actually watch you code. Alternatively, you could start by volunteering at a startup and gaining the relevant experience, or take a course from a school like Coursera, General Assembly, or your local university which will teach you more formal principles. Hope this helps.