I sell guitars and amps on eBay. I get good money and the competition isn't too bad, but I would stay away from electronics and jewelry. Electronics change too quick (I started with them before guitars). The problem is EVERYBODY wants to do electronics and you have to constantly sell. You cannot afford to hold anything without your items loosing value. The more you buy, the more you save comes into play. In order to make it real worthwhile, I have a semi truck backing up to my house. With several thousand invested in guitars and amps (most of which are the same model) I cannot list them all at once (I do this by myself). From what I found out, listing two items at once goes for far less than one item at a time (the items being the same). If there is only one, it seems like there is less of a supply so the buyer will bid higher. Otherwise, they wait for a good deal.
As for the fun of answering questions, you will QUICKLY realize half of eBay is full of morons and idiots. I get stupid questions like "Do you have a better picture? the glare makes it hard to see what kind of wood the guitar is." When in fact the only "glare" is a reflection from the paint and clear coat...there is no exposed wood. Unless I could take an x-ray picture through the paint, I will never be able to get a good picture. I get emails from people who have their own website and I get a list of stuff I should do because he has his own website. Stupid tips about how to take pictures because he has his own website. I never got an email from that guy that didn't start out "I have my own website". I get emails about items being broken, so I tell them to return. Their response? "No, I don't want to".
eBay if pretty good once you find the right supplier, but remember, nothing sells forever. Unless you want to start off big with a reseller's license and bulk wholesale orders, it takes a while to find a good supplier. One of the best ones I had was from a guy who did the exact same thing as me, but did the wholesale thing (before I started doing it). I would buy a lot of stuff off him for a good deal because he couldn't order anything unless he met the minimum (something like $5,000). A few years ago when NJ got hit with really bad rain, he pretty much lost everything and decided not to get back into it. That was a real blow to me, but I eventually found another supplier.
One last tip, you need a supplier that has good customer support. People are going to complain to you and you have to fix it. More than likely, it is either by replacing damaged items, or helping them figure out what to do with it. You need someone that will help fix problems. I got a few things that ended up with missing pieces. I was glad when I got them priority mail two days later.
