Section 21. If a condominium does not contain any unit which is designed for occupancy by only one family or household, or if the floor area of all those units which are designed for occupancy by only one family or household does not in the aggregate exceed ten percent of the floor area of all units in the condominium, then the following provisions shall be applicable notwithstanding any other provisions of this chapter, and such condominium shall be considered a commercial condominium:

(a) The by-laws may provide:—

(1) That to any extent specified in the by-laws the common profits shall be distributed among, and the common expenses shall be charged to, the unit owners in proportions other than according to their respective percentages of the undivided interest in the common areas and facilities.

(2) That to any extent specified in the by-laws the unit owners shall not be personally liable for sums assessed for their share of common expenses, but such provisions shall not adversely affect any lien for said share.

(3) For limitations upon the first mortgages of record or the types or categories thereof which shall have priority over the liens provided for in clause (c) of section six, which may be dependent on the person or entity to whom such mortgages are given or upon such other criteria as may be specified in the by-laws.

(4) A procedure for submitting the disputes arising from the administration of the condominium to arbitration or other impartial determination.

(5) Provisions giving a particular unit owner or owners voting rights with respect to election of directors, trustees or members of the managing board less than, or in excess of, the voting rights which such owner or owners would otherwise have had, and provisions requiring or permitting approval of any matter, or any specified category or categories of matters, by a proportion greater than a majority, which proportion may be as great as one hundred percent.

(6) Terms and conditions differing from or exempting the condominium from subsection (c) of section six, subsections (c) to (k), inclusive, and (m) of section ten, and sections seventeen, eighteen, and nineteen, or any of them, regarding limited lien priority for outstanding common expenses, payment of outstanding common expenses by tenants, rebuilding made necessary by fire or other casualty loss, the making of improvements and the allocations of the costs of such rebuilding or improvements, and the removal of the condominium or portion thereof from the provisions of this chapter; and in such case such terms and conditions so provided in the by-laws shall take precedence over such provisions of said subsection (c) of section six, subsections (c) to (k), inclusive, and (m) of section ten, and sections seventeen, eighteen, or nineteen to the extent inconsistent therewith.

(b) The master deed:—

(1) Need not contain a statement of the number of rooms in any unit designed for purposes other than dwelling.

(2) May contain a requirement that in order for instruments to be binding on an organization of unit owners which is a trust or unincorporated association, such instruments shall be signed by a greater proportion of the trustees or of the managing board than a majority, which proportion may be as great as one hundred percent; and in such case the provisions of clause (e) of section ten shall apply only to instruments signed by the proportion of trustees or of the managing board set forth in such requirement in the master deed.