Depends on the trade, you can't make electrical work without some form of recognition I believe. And beyond that I mostly asked regarding customers, you want something to back your claims and prices.

Those are called “trade schools” in the US, and most community colleges have programs for trades. For example, a lot of community colleges have programs in auto repair and heating/cooling.

It gets more complicated in the US because of unions. In many places, you can’t become a plumber or electrician without an apprenticeship, which is controlled by the trade unions. Therefore, community colleges might offer classes on plumbing or electrical, but there’s no equivalent to a certification program, because it’s not possible to become a professional just by going to school.

Interesting I never linked the name 'trade school' with adult learning. I thought it was some parallel track for teenagers to jump into a field.

Depends. If it's in a medical field, you might need a degree.

You don't need a degree to open a medical business. You need a degree to practice medicine.

This certainly depends on local rules. For example, in the UK I believe dental businesses can only be opened by a qualified dentist. I was surprised when I learnt this earlier this year.

This source [0] says “non-dentists cannot set up or buy dental practices as an individual or partnership but they are permitted to be shareholders of a limited company which owns the practice” and “the majority of directors of that limited company cannot be non-dentists”.

[0]: https://www.plutopartners.co.uk/post/who-can-own-a-dental-bu...

I believe this is the case with law firms, and probably some other professional firms, in the US as well. AFAIK a law firm is a partnership of lawyers.

That said, this isn't what most people are talking about when they are talking about starting a business.