Massachusetts General Law Chapter 183 Section 6 allows a condo association to initiate a collections action for past due condo fees after 60 days deliquency. Section 6B states that the unit owner is personally liable for all sums assessed including penalties, interest and all costs of collection - which includes attorney's fees, costs & charges.
If the unit owner has a mortgage, the lender should be notified and likely will pay for the collections amount and costs, as the association has the right to place a lien on the unit should the owner fail to pay. This lien will be superior to the mortgage, which the lender will want to avoid.
Contact an attorney who hs experience in this field as soon as possible.