Porn, drugs, or gambling. ;-)

Joking aside, I think the easiest way to make $30k after taxes is to drastically cut your living expenses and save $30k. To make $30K after taxes, you'd have to make close to $50K before taxes (I assume you have a decent programmer's salary already, and this'll put you in a high bracket). There aren't many ways to make $50K in a hurry without a long ramp-up period. If you could, everyone would quit their day job and make their freelance business their real one.