Selling Books for a Living

I have been selling book sonline ofr over 5 years now. I have been doing it part time and finding that is not bringing in a great deal of money. It is making me just a bit of pocket money really which is why I am now doing extra things to earn money as well. I often wonder how book shop owners manage to keep going when they have far larger overheads and have to hold more stock. I have always liked the idea of owning a book shop but I do not think that it would be a worth while business move for me.