You need to start by selling things you have around the house. This way you'll get a feel for how to list, what kind of shipping services to offer, what price to start bids at etc. The when you've exhausted all that try thrift stores, yard sales or move on to pallets.
Yep, completely agree.
List some older unwanted gear from around the house, then move onto markets and charity stores. You will find your outlay to be quite low when dealing with Secondhand items through these channels, and you should be able to make good margin if you buy right.
Definitely worth taking a look any local auctions you have in the area also, never know what little treasures you come across there.
Of course ebay is just one option, spread your advertising around. Some other auction sites may not have much traffic at the moment, but that also means that they have great rates to list.
Use your free classified options, Craiglist for online, but check your local papers to see what options you have there as well.