Ebay selling

Anybody out there do any selling on ebay with any amount of substantial profit? If you have successfully set up an ebay business that is making you money, could you please offer some pointers... in particular about keeping costs down? What do you sell? How did you decide what to sell? Is listing time really a factor? Do extra pictures help the final price? How do you protect your self from predatory buyers? (People who pay by paypal and then complain to get their money back) Do you charge a packaging and shipping fee? Do you advertise outside of ebay? What kind of listing works best for you (fancy type styles? extra pictures? etc)?
I am working toward my own financial independence and was looking at ebay as a possible income stream. Any help and or suggestions from veteran ebay sellers would be very much appreciated. Thank you and have a great day!