the short answer
Hire a coach - not just a VA - when demand consistently outstrips the hours you can personally deliver well and your delivery is documented enough that a new coach inherits a process, not guesswork. From there it is a repeatable sequence: vet for philosophy fit (not just credentials), agree on a clear pay structure, train to your written standard, hand clients over with a warm introduction, and quality-control with check-in audits and scoped, role-based access.
This article is general information, not legal or HR advice. How you can classify and pay someone - contractor versus employee in particular - varies by country and state, so treat the structures here as a practical starting point and confirm the rules for your jurisdiction with a qualified professional before you rely on them. Keep scope of practice in mind too: if a client needs support beyond what a coach is qualified to give, that is a referral to a licensed professional, not a reassignment to another coach.