As a business management professional, I can tell you right now that idea won't fly. Why? Because just like how you find yours suppliers online and have them sell you stuff for cheap, so will your potential clientel. On top of that you will run into that issue that you described where online stores won't sell to you unless you have an actual location because you would be their competition, or more accurately, an annoying fly on the wall because you won't be able to compete with their prices anyways.
The market is saturated already and the competition is strong.
My two cents.