Hey Madi, likewise, wishing you well.
You have mentioned the practicalities of carrying out the primary role of the business, which is obviously your passion, but you have not mentioned whether you will be a self employed sole trader or wish to give your business a more formal footing, like a limited company; remember you will have to be 18 before you can enter into formal contracts legally, this includes your contracts/policy documents with clients.
You will have to register with HMRC as self-employed and will have to complete a tax return each year. A business bank account is a good idea, or even a separate personal account (if you wish to keep it simple, which is a good idea st the outset) to keep all business transactions separate from personal spends and you will have to keep meticulous records for tax purposes.
Have you thought about the insurance you will need and have you costed this? If it's a big expense, consider what courses you could take to show your expertise to reduce this cost.
There are so many free courses/resources for aspiring self employed folk around these days. Do check out all the free and cheap resources available to ensure you start out on the right footing and don't end up financially compromising yourself.
The job centre and various charities offer free resources to educate yourself and ensure you're on the right path; also the Open University offer free courses and check out local FE colleges too.
You certainly sound motivated Madi and I wish you the very best, but please take this time before you turn 18 to educate yourself about your potential liabilities and absolute responsibilities as a business owner first.