I predict that I will have 100k by the end of next year at the current rate of sales.
And you do not assume that you need an accountant which would explain that to you? Btw., depending on jurisdiction you may also need a LOT of paperwork from your legal guardians because a 100k merchandise operation is not pocket money, and you may or may not be of legal age.
Also, could you let me know if there is less tax for minors who are sellers?
Why would the government make special provisions in it's laws for minors? Because either rarely any minor runs a successfull buyiness (hint: that is the case) then none does even THINK about putting in special cases. Or TONS of them do - then how stupid would it be to tax them less?
General rule is that taxation is per person, regardless of age. Minors normally do not pay taxes due to not having enough income to do so.
I wonder if anyone has any ideas of what to do when you are starting out.
Yes. Get professional advice. Fast. Taxes are tricky - making something wrong means you pay fines, and that is pretty much regardless of age. Also you want arms length - if a paid accountant makes a mistake, you are not at fault and can proove it, which is relevant for possibly criminal isues - and his insurance will cover the damage. I once had an accountant (that we sort of bankrupted) that had to go to the government and correct his accounting for 2 years. The fines where not funny - his insurance totally did not like it. Closed shop closely after. Point is - if it would be me, they would ahve doubts about my ability to run a business and it would possibly have criminal consequences (failure to keep proper business documents in order). With the accountant it was "arms length". I pay a chartered accountant, I can assume he is competent.
You likely will find out pretty much that 100k in merchandise is not a lot. Unless you make a LOT of margin (difference between sales price and purchase cost, in simple terms) there is not a lot of money left once you restock that is actually a profit.