Not legal advice. Ask a revisor before you register anything.

Write down every project that earns money and where that money lands. Ask an accountant (revisor): sole trader or ApS, when VAT (moms) registration applies, and what bookkeeping is required. Keep a separate business account and contracts in the company's name. Under 18, there are extra rules; check them before you start.
E Evidence: built from practice. What works for coaches and practitioners. Labelled that way.
Danish secondary legal sources. Not legal advice: verify on virk.dk and with a revisor.
Not medical, legal or financial advice.
In The Ecosystem every framework comes with a daily action, a room that checks in, and the full library.