I translate software (GUI and Help) mainly for two software developers, translate tutorials and snippets to be put on websites, and occasionally ask a developer, if he wants help with his sometimes adventurous translations.
Additionally, I am the usual Mr. FixIt, when computers in my vicinity (friends, family) are broken or have to be replaced by new machines.
Via mouth to mouth propaganda, friends of friends ask for my service, so that's where serious money (fixed sum per hour) comes from.
As I have a fulltime employment, all this freelancing is done after hours, but gives enough additional income to make it worth the time.
Employer and IRS are informed about my status, so I have a go from my boss and taxes are paid from the freelance income, too, but in a very complicated calculation.