I've had experience with this one and would recommend determining one thing that gets you fired up and would also let you offer something to the world which the world would love to pay you for..

For me, this has turned out to be something related to forming a virtual team and letting my team work on the time-consuming tasks and I'd just be managing them, making sure they deliver quality services to clients. This has cost me a minimal up to none at all (investment) since what I just need are reliable team members/staff and me posting ads on job sites regarding our services or through Odesk..

That has worked for me.. But primarily that would really depend on your interests/niche. :)