How to start a marketing agency?

I'm 18, still in school, and I want to start a marketing/advertising/business image agency.

I've always been good at breaking things down and getting to the root, I'm good with my choice of words and I know how to 'work people'. I get asked by people (teachers, friends, family, family friends etc) on how to portray myself/my business better, how to word a certain document better or just general how to give others a better impression, (I do a lot of the marketing/advertising for my fathers iPhone repair business) I'm also told I've a talent or knack for understanding people as a whole or just an individual and knowing what they want or what they mean to say.

Here, in Ireland, there is a masters in marketing but no degree (you must do a business degree and specialise in marketing), I don't particularly want to wait that long, nor to I particularly want go to college unless it's 100% necessary.

I want to own my own business, I want my success to be determined by my efforts.
How does one go about starting such an agency?

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