the ones that make money are the ones that get collectibles/antiques cheap at auctions. lots and lots of work. the shipping and collecting money is a big pain in the ass.
in 98 i gave it a (part-time) shot to see if i could make any money if i HAD to. all i did was buy sports collectibles on ebay and resold them for a higher price, with a better ad

most have gotten good at the ads now, with all the software available and people getting better using their home pc's.
some of my good hits...
i bought 36 griffey signed baseballs for $10 each and sold them for an average of $50 each.
bought a mike tyson signed glove for $95 and sold it for $450
bought a poker machine for $120 and sold it for $650
i did it for a couple of months and made about 2 dimes a month just playing around. would never want to do it full time but if push came to shove, i know it can be done.
look at some of those power sellers with 10's of thousands of positive feedbacks. they must do okay.
just figure what you want to make and do the math. you want to make $1000 a week you have to sell 10 items where you make $100 each or 20 items at $50 each or 1000 items at $1 each. i think the best way is to pick glassware up at auctions for cheap and sell high.
who knows.
good luck!