I really don't want to pour water on your bonfire as I love your enthusiasm but I work for an online shoe shop and at the moment the market is saturated. We sell thousands of different styles, colours, makes and sizes but still customers want more.(We work out of a 3 storey building!!) If you have a very unique brand or you make/decorate the shoes yourself then this is different but if you want to sell a certain make of shoes such as Lotus, Sketchers,Ecco or Van Dal (something you could get in a shoe shop) then you will honestly struggle. A good benchmark is to go to google and enter the name of the brands you would like to stock. See how many websites are already out there. then you know how many you have to compete with.
I am sorry if you feel I am trying to put you off but I want you to be aware that selling online is hard. All the research in the world won't prepare you for how cut-throat it is. You website has to be bigger, better and more sparkly than the last one they looked at or the next one they go to. The front runners will pay good money to make sure your website doesn't get the exposure it needs. And if you ARE selling a certain range of shoe they will try to shut you down. You need to deal with the manufacturers directly or they can demand you don't sell their shoes on a site that isn't endorsed by them.
If you are selling something unusual or not readily available in the Uk then happily you can dismiss my negativity and I wish you all the luck in the world.
4 Years working for an online shoe retailer