No matter what state you live in, you are required to report income from online transactions (on your federal return, and state if your state has an income tax). MA just has a lower threshold for the transaction processor to provide a 1099-K.
(For anyone else who comes across this thread, a one time transaction is not necessarily a business. If you made a profit on items you sold but are not running a business, you could report the profit in the Miscellaneous Income section, as "Other Reportable Income".)
