was $2,000 from self employment or W-2. if self employment you need to file a return to pay self-employment tax - applicable when net SE income over $400. If W-2 you would need to file if there was federal withholding that you wanted to get back - if your sister can claim you, you'll need to indicate on the return that you are the dependent of someone else and you do not claim your son. either
who supported you? your sister must have provided over 1/2 the support for you and your son. support for each of you is determined separately.
