I'm in the South West and charge £35 an hour for regular maintenance (min 2 hours).
For one off jobs like garden refurb, laying out new gardens, getting a garden ready for a house sale for example I charge for the finished job rather than by the hour. I found I was charging by the hour and the finished result looked worth much more than it had cost.
For materials and plants I have a trade account with my brilliant local garden centre. They give me 10% discount and I add charge my clients full price plus 10%.
I run a van, am insured and provide all my own tools, fuel etc.
@MrAlyakhin said about providing a garden advice service. I do this, especially in winter. IDing plants, explaining about their care advising on how to improve lawns, providing lists of plants that will thrive in the clients garden soil and orientation, teaching people how to prune etc. I love that side of it. £70 ph. A designer would be much, much more expensive.
I hope that helps but do please DM. I'm happy to help.
@SherbertsHerberts Yes, I'm busy all winter. People do major refurbs then and there's always masses of maintenance. My January is almost all pruning. I have two weeks off at Christmas but otherwise it's full on 12 months of the year and there are as many people on my waiting list as I have clients on the go.
Most of my regular clients are lovely elderly women who have adored their garden but find it too much now. They bring me tea and coffee on breaks and often sit with me or work alongside me whilst I'm gardening. They've all become friends really. It's a fantastic way to earn a living.
About the fear. Don't have any. I sort of envy you the start up @Dolphin78 because you have a thrilling time ahead of you. The RHS course is wonderful and you'll meet great people there from all walks of life.
There is a lot more work available than good gardeners to do it. You'll thrive.