From: artie131
Personally, I order fake stuff from manufacturers and sell them for 100%-200% profit (depending on how long you would like to wait for each sale) on craigslist.
Fake stuff like Coach, Prada, ect…?
Some things that I used to do with my dad, but are no longer worth it.
-Handcuffs: Buy on eBay or from Smith and Wesson, people will pay stupid money for them for sex
-Steering Columns: used to be able to go get 10 of them at local junkyards for $50 to $75 and sell them for $100+ each!
-Gun stocks: Buy old M14/M1A1 gun stocks and refinish them! 10 for $300 typically could net $300 each once refinished!
Just anything that seems like there is a hole in the market for it. Personally I would shy away from things involving to much technology because it's always out of date.
Another thing I might get into over the summer is AR15/M16 parts, but you need to be knowledgeable to make any money with it!
E: Of course some of these things might make you or loved ones uncomfortable (guns and gun parts), or they might even be illegal in your state/country! Read the laws first!
E2: Just noticed you live in California, so most of the profitable guns/gun parts are out for you, but look into AR15/M16 stuff! Depending on the area you live in, it might be really really profitable!