I looked into doing this and decided to give photography a try. I had a few friends who didn't really put a value on photography so they were the perfect subjects to start developing a small portfolio for weddings and I invested in some equipment. As I had some kit I then developed a photobooth for less formal events, paying out more for hardware and props. Potentially a good little earner as the hardware was cheap and the only costs was printing paper and replacing the odd prop. Didn't have time to develop on this as I then got an opportunity to give motorsport photography a go which is what I wanted to do, so again invested in more kit as the wedding lenses/bodies wouldn't cut it and off I went shooting.
Probably invested 10k in kit and made 2k
(that is the right way round right?)