It would seem, that what I found would suggest you must wait nine months to a year before working off-campus. I am not an immigration specialist or officer but I imagine freelance employment constitutes "off-campus" employment. You would be better off contacting an immigration agent or your school directly. In any case, you'll need to contact one of them to acquire the "[special] authorization" which is suggested.
F1 students may seek off-campus employment if they meet certain requirements. There are several options for off-campus employment, but these general rules apply:
- You must be in legal status to apply for off-campus employment;
- You have been enrolled on a full-time basis for one academic year (generally nine months);
- You must apply for and be granted specially authorization;
- If you are still enrolled in a full course of study, your combined on- and off-campus employment may not exceed 20 hours per week when school is in session;
- You still remain in F-1 status even if you are working full-time for an employer.
Pulled from : http://immigrationroad.com/visa/f1-student/f1-student-visa-employment-options.php
Note that the last two bullet items conflict with themselves. Full time employment is 40 hours per week... well above the previously mentioned 20 hour limitation. With that in mind, in addition to the clear grammatical error, you should seek further advice from an accredited source.
I think this question is far more about immigration and an F1 visa than it is about freelancing.