I think you definitely need to put a lot of time into stock photography if you want to make any money.
You need to research the best-selling types of photos, then have the gear, expertise, locations, models and time to take sufficiently-good-quality photos, and then submit a lot of photos on a regular basis to stock agencies.
There is certainly money in stock photography - if people like Uri Arcurs can make enough money from stock photography to run a large studio with 12+ full-time employees, then it's definitely possible ;-)