"NEW SECTION.  Sec. 1   A new section is added to chapter 36.70A RCW to read as follows:
     (1) As used in this section and section 2 of this act, "first-time buyer housing affordability index" means the index determined by the Washington center for real estate research that measures the ability of a typical renter household to afford the purchase of a typical starter home by assuming: (a) The household will purchase a home priced at eighty-five percent of area median household income with a ten-percent down payment; (b) the home mortgage loan is for a term of thirty years at the prevailing average fixed rate of interest; and (c) the potential first-time home buyer earns seventy percent of the area median household income and twenty-five percent of household income can be used for principal and interest payments.
     (2) A first-time buyer housing affordability index of: (a) One hundred, indicates that a household of the defined income can afford a home of the defined price; (b) less than one hundred, indicates that a household of the defined income cannot afford a home of the defined price without spending more than twenty-five percent of their income on mortgage payments; and (c) greater than one hundred, indicates that a household of the defined income can afford a home of the defined price while spending less than twenty-five percent of their income on mortgage payments.

NEW SECTION.  Sec. 2   A new section is added to chapter 36.70A RCW to read as follows:
     (1)(a) In any county planning under RCW 36.70A.040 in which the first-time buyer housing affordability index, as defined in section 1 of this act, and as determined by the Washington center for real estate research at Washington State University, is less than one hundred for three quarters in any year, the county may permit single-family detached residential development of any density outside the urban growth area designated according to RCW 36.70A.110 for the following two years. Single-family detached residential development authorized under this section is not considered urban growth located outside of an urban growth area. Services provided to a single-family detached residential development authorized under this section is not considered urban services located outside of an urban growth area.
     (b) Any county planning under RCW 36.70A.040 and permitting single-family detached residential development under (a) of this subsection may:
     (i) Change its comprehensive plan and development regulations after the determination in (a) of this subsection has been made by the Washington center for real estate research to provide new locations for or increased density of single-family detached residential development under (a) of this subsection; or
     (ii) Incorporate sections in its comprehensive plan and enact development regulations that provide new locations for or increased density of single-family detached residential development that are contingent upon a determination under (a) of this subsection that the first-time buyer housing affordability index was less than one hundred for three quarters in any year. If the county chooses to enact sections of its comprehensive plan as well as development regulations, the county may provide that these sections and regulations take effect January 1st of any year following the determination by the Washington center for real estate research under (a) of this subsection.
     (2) The one-year period measured by the Washington center for real estate research under subsection (1) of this section begins and ends in the third quarter of the calendar year. The time period for which the ability to permit single-family detached residential development under subsection (1) of this section begins January 1st of the year following the determination by the Washington center for real estate research under (a) of this subsection."