I'll chime in as someone who sells stock.......Photography is my sole source of income and I use stock as something to do when I have nothing else to do. It can (and does) earn a little extra money for me......just to give you some perspective, I think I've earned about $400 over the last two months after commission fees.....not much but I'll take it. Some months I get nothing, other months I get a nice surprise. That said, IME, making any money and realizing regular sales with stock images takes a huge library of quality salable stock images that number in the thousands. It takes quite a bit of time to get things rolling.
When I shoot stock, I take the time to put together a plan to create images that I think have selling potential.....simply uploading a hard drive of all of your useless images you have no need for will rarely create sales. It takes time and commitment along with a vision for what's in demand.....and even then, the payoff is pretty small. IME, for most people, getting a part time job delivering pizza's or bagging groceries would be a better way to make a few extra bucks......at least there, you're guaranteed an hourly wage.