Write up a case study on how you made a business $MONEY using your iOS programming skills, submit to HN.

Contact other iOS freelancers, particularly those who appear to be doing well, and ask if they could provide you referrals for overflow work or work which does not fit their interest (wrong budget, wrong client pool, wrong location, etc).

Cold call or cold email people. Dirty secret: it works.

Work your offline and/or online social networks, asking people if they will warm-intro you to business owners who fit the general profile of "People who could conceivably write very small [+] checks."

[+] This goes against everything in my upbringing and what I believed about the world as a college student, but it is an important lesson for technologists to learn very early in their careers: $4,000 is not a lot of money to many businesses.