Do I have to pay taxes on freelance income (<$2000), provided I already have a full time job?

It is usually required for all income sources and earnings to be reported. This is your prerogative to declare accordingly or decide to fund a charity of your choice instead.

By right, everything need to report. But i know most people dont, as there is no way to track. Especially when transaction is by cash and no reciept l/invoice.