You have been selling a reasonable number of items each month including jeans so you must have a bit of an idea what you are going into. But wow, five thousand pairs of jeans is going to take some serious industrial style storage.

I have around 2000 listings of mainly small items and currently use one room in the house and a two car garage fitted with industrial shelving. This covers the listed items. I also have a rented storage shed and a shipping container fitted with industrial shelving to store surplus unlisted items.

My suggestion would be to find out how large clothing shops, store their unsold items in the back rooms. Go to closing down sales or auctions and buy up the storage systems to fit into your shed, house or whatever you decide to use. There is a lot of thought gone into the design of these systems so why re-invent the wheel.

As others have mentioned, keeping stock organised and easily accesable is essential to running an efficient ebay business. Good luck with the business expansion.