You can start a legal procedure against the person who is not paying. I would recommend enforcement proceeding rather than litigation initially. The manager (yönetici) or the president of the Board of Directors will be entitled to represent the entire apartment building in this case. He or she is entilted to resort to legal action by law, but I would still recommend that the Condominium Owners Committee takes a resolution empowering the manager/president to that regard and to appoint a lawyer as well. The Notaries seek that resolution mostly to see if the manager/president is allowed to grant power of attorney documents.