lets not dash the chaps hopes. If your willing to do you homework then there is no reason why you should be able to open you own store.
1) You need the experience so go and work in a store similar or bigger than the one you are hoping to open. Tell management of your intention and i'm sure they will try to accomodate you. If your willing to put in the hours i'm sure they will show you the back room logistics to buying, marketing and selling.
2) You will need a lot of cah in the bank, another reason to get a job.
3) See your bank manager, if you have a good well prepared bussiness plan you will be able to get a small bussiness loan. But remember one rule: "there is always, always someone willing to lend you money", so if your bank says no, there will be one that says yes.
4) Be prepare to work like a bugger for the foreseeable future
5) Keep a good credit rating at all cost, you need a clean rating when squeezing us suit for cash.
One very important question is are you wanting to be self employeed? or work for someone else? Remember being self employyed may sound glamourus but it is a lot of work and you may be able to earn more working for an employer.
Its interesting that your first suggestion was to open a store. That suggest that either it is a subconsious disire OR it was the first thing that came to mind due to a lack or research. Maybe you should chat to your career counsilor, they are a lot more useful than you may think.
Maybe you should consider IT project management roles, these will give you a more top level approach to IT rather than the hands on stuff.
If your adverse to coding then that knocks out a lot of IT consultancy. Coding doesn't need much maths knowledge, maybe you could look into it for uni / college
Are you considering going to uni. If so you choice of subject will have impact on you future career, if you hoping to set up on your own then something mixed with compsci and business management.
Try to address some of these questions and you may get a clearer picture