Start from what you have
Most niche advice asks what you are passionate about. That is the wrong first question, because it ignores the only thing a buyer checks: whether you have any reason to be credible about their problem. Start from your raw material instead.
Why background beats passion here
The single biggest cost in a new coaching practice is the time between starting and being believed. A relevant background collapses that gap. It is why a former HR director sells career coaching in weeks and a career-changer with the same certificate sells it in months, or never.
This is also why the deepest seams stay profitable. Executive coaching is not better work than life coaching. It is work that far fewer people can credibly claim, and the fee reflects the scarcity rather than the difficulty.
Passion still matters, but it decides which of your available seams you pick, not whether you can ignore the list.
The three questions that actually narrow it
Who signs the cheque? An individual paying from their own money behaves completely differently from an employer paying from a training budget. Employer-funded work is a slower sale at several times the fee. That one choice shapes your pricing, your marketing and your calendar.
What do you have to do every week? Every seam comes with a channel attached. Executive work means LinkedIn and conference rooms. Health coaching means Instagram, indefinitely. Pick the one you can sustain for a year without resenting it.
What happens when it works? Career coaching succeeds by losing the client. Executive retainers succeed by keeping them. Those are different businesses with different economics, and the difference shows up in year two, not year one.