Affiliate Marketing Secrets

I need some help figuring out what I can sell on a website I want to create. I do not want to do affiliate programs, and all that..I want to sell actual products. I am 17, and I am into military stuff (i.e. guns, gun accessories, military apparel, military accessories, etc.) I am also into video games….but take note…again I am 17 YEARS OLD…no expendable/disposable income…NOT A LOT OF MONEY. Any cheap business ideas for a 17 Year Old would be appreciated…tanks.