Section 13. All claims involving the common areas and facilities shall be brought against the organization of unit owners, and all attachments and executions related to such claims shall be made only against common funds or property held by the organization of unit owners and not against the common areas and facilities themselves other than the leasehold of any lease included therein. After such common funds and property have been exhausted, individual unit owners shall be liable for the balance due, if any, provided, however, that the amount for which a unit owner is liable shall be limited to a sum equal to the amount of his percentage interest in the common areas and facilities times the balance due.