A couple of friends of mine needed to generate a little extra income on top of their wages. They were both into keep fit and enjoyed working out. They decided to supplement their income by becoming part time fitness instructors.
They had to do a course which lasted less then six months and taught them the basics of keep fit. They both enjoyed doing the course and made some great friends along the way.
The money is good and they keep fit at the same time! One teaches spinning on the stationary bikes whilst the other does aerobics classes. They both benefit from free membership in the gym they teach in
If you are good with your hands and into DIY then why not become a part time handy man? Busy people now a days just never get round to fixing that faulty cupboard and the money that they are willing to pay for odd jobs is not that bad either for a couple of hours work.
Start up costs are very low as long as you have the full range of basic tools. Most people who start out working part time find that this can easily turn into a full time occupation!
Do you enjoy gardening? This is a great little earner if you do not mind getting your hands dirty...