Self employed

How about losses.  Using the tickets again, if the cost is $200 per ticket and I sell these for $100 each through a ticket exchange to get rid of the inventory, it's still going to report the $100 sale to my 1099K.  What do I need to do to ensure I'm not getting taxed on this?

 

Earlier there was a comment about paperwork or not if I sell for profit.  What's a best practice for my wife and myself if we are selling things like clothing, tickets, collectibles on the side for a profit.  At least have an business DBA even if we don't need to register?  (ie. Josh's Collectibles"