Why not have an unrelated day job? You can always use your creative skills in your free time to make your 'contribution'. Use your day job to fund your weekend missions and your purpose. Maximise the money during the day = do more good work at night.
You could make and distribute posters that raise awareness for something, or start and promote a new webcomic that is great fun and entertaining and also champions an important positive message, approach local small-time charity organisations and offer them free graphic design work, help friends and family get their business ideas and ventures started with graphic marketing and free logos etc, publish an indie magazine and distribute it at local schools/colleges... you know... ANYTHING. Use some imagination, dude.
