Any decision having long term financial implication cannot be approved by Secretary or MC, it require approval of AGM. This is clear of fraud which need to be brought to the notice of Registrar seeking appointment of auditor. There can be other irregularities by Secretary in collusion with then Chairman which has not come to light. Common areas are property of all, it can never be sold. Make a online complaint to the Registrar. This is case for appointment of administrator/Auditor by Registrar.