Missions randomly pop up on Crime.Net. You might need to be a bit higher level. I'm pretty sure at level 10, you unlock access to new missions. --- Hey, everyone! This store discriminates against the poor!
I can also confirm that level 30 unlocks new jobs. I just hit it right now and that was teh announcement it gave me --- So he said, "Do you love me?" and she said, "No, but that's a real nice ski mask!"