Attorneys who specialize in bankruptcy or estate settlement will have clients who either need money or have items to sell. By partnering with attorneys in your area, these attorneys can refer business to you. If you sell on consignment, you can make a nice commission selling items for people who are in the process of filing for bankrupcty, or who have estates (used and vintage items, possibly antiques) to sell.
The only way to have a successful eBay consignment business is to treat it as a business - to have a steady stream of repeat customers who depend on you for helping them turn their items into cash. Selling on consignment for your family and friends doesn't really work. There are too many emotions involved and usually not enough merchandise to make it worth your time. eBay selling may seem easy to you, but most people won't take the time and effort to learn how to do it.
There are other types of businesses you can partner with such as charity thrift shops and small mom and pop type operations just to name a few. It costs these businesses nothing for you to try to sell their items online. The key is that you (the consignment seller) will only spend your time trying to sell items that you KNOW will sell. Sometimes, you will have to say "no" because the item is not profitable and you are not going to spend your time trying to sell it.
I can speak from experience here. I have a consignment contract with a local Humane Society to sell items from their thrift store. I have been educating the staff on the types of items to pull out and set aside for eBay and Amazon sales. I can get 5 - 10 times more for an item than the thrift store can get because if their limited foot traffic. I drop by the store about twice a week, pick up the items, take a look around, and list the items on eBay for them. The staff loves to see me come by because I usually bring them a check! And I love working with them because most of the items I choose will sell for between $50 and $200. So I can make $20-$30 an hour selling items for somebody else who has a plentiful supply - I don't have to go out and cherry pick these items myself from all over town.