I think if you only work on your online store part-time you will not be completely successful. Competition in the online marketplace today is brutal and fierce. I don’t see how you will be able to successfully compete with sites and stores like Amazon and eBay if you only work at it part-time. Even then, it might be tough to compete.
Amazon and to some extent, eBay, has changed customer expectations for quick order processing, product shipping and communication. Customers just don’t have patience like they used to. What is the old saying, “Go big or go home?” I think that is appropriate in this case.