I got into maths tutoring about 6 or 7 years ago. I focussed on teaching A-levels, I volunteered for Action Tutoring (though they only taught up to GCSE). I joined some tutoring sites and began by answering the job requests that came up setting my prices quite low at first -- I also started with very few students because I wanted to make sure that I could prepare thoroughly for their questions. As I gained experience and reviews, I slowly moved up the ranking lists and started to get enquiries and could build from there.
There was, with some exceptions, very little interest in my qualifications or degree. What mattered most was how the first few tutorials went, whether the student felt they benefited from the tutorial. It may be different if you're teaching younger students,but at A level, the parents weren't as involved in the process as I thought they would be.
However, I think the market may be tougher now than it was. The tutoring site I had got most of my students from hiked its rates abruptly a couple of years ago - it takes about 35% of the fee for every lesson now whereas once it took a much more reasonable 20%. Plus chatgpt is getting very good at answering A level maths questions (although it will still bluff its way confidently to wrong answers in certain cases), and I think that's going to make a difference. All my students at the moment I work with directly, without an agency -- but I'm still having to find ways to advertise and attract new students every year.
The main A level boards (Edexcel, AQA, OCR) have a lot of free information - syllabus, past papers, recommended textbooks - a lot of the textbooks can be got second hand for decent price, and I ploughed through a couple of them before I began teaching for real - despite being good at maths, I found I was quite rusty.
That said -- I've really enjoyed the job, being my own boss, being allowed to drop students who annoy me (there have been some - though most have been great). And it's nice to get back to the actual teaching - doing the part of the job that really matters - without all the paperwork, arbitrary rules and checklists that goes on now both at school and university.