When do I need a Disclosure Report (Public Report) to sell lots in a subdivision that has existed for many years?

By law, A.R.S. 32-2101(56), means any person who offers for sale or lease six or more lots, parcels or fractional interests in a subdivision or who causes land to be subdivided into a subdivision for the subdivider or for others, or who undertakes to develop a subdivision, but does not include a public agency or officer authorized by law to create subdivisions. All subdividers are required to obtain a Disclosure Report (Public Report) prior to offering lots for sale in accordance with A.R.S 32-2181 et seq. and Commissioner's Rule R4-28-B1207.

It is the act of selling that requires a Disclosure Report (Public Report), not ownership.  There is no time limit connected with this requirement. Upon acquiring fee title or an equitable interest in the 6th lot within a single platted subdivision, a Disclosure Report (Public Report) is required prior to its sale. You could purchase and sell 2 lots every five years and as soon as you acquire an interest in the 6th lot and offer the lot/lots for sale, you would be in violation if you did not obtain a Disclosure Report (Public Report). If you hold fee title or an equitable interest in 6 or more lots at one time, a Disclosure Report (Public Report) is required prior to offering any of the lots for sale.