(1) Any city, town, county, or municipal corporation that is required to develop a comprehensive plan under RCW 36.70A.040(1) is authorized to require, after reasonable notice to the public and a public hearing, property owners to provide their portion of reasonable relocation assistance to low-income tenants upon the demolition, substantial rehabilitation whether due to code enforcement or any other reason, or change of use of residential property, or upon the removal of use restrictions in an assisted-housing development. No city, town, county, or municipal corporation may require property owners to provide relocation assistance to low-income tenants, as defined in this chapter, upon the demolition, substantial rehabilitation, upon the change of use of residential property, or upon the removal of use restrictions in an assisted-housing development, except as expressly authorized herein or when authorized or required by state or federal law. As used in this section, "assisted housing development" means a multifamily rental housing development that either receives government assistance and is defined as federally assisted housing in RCW 59.28.020, or that receives other federal, state, or local government assistance and is subject to use restrictions.
(2) As used in this section, "low-income tenants" means tenants whose combined total income per dwelling unit is at or below fifty percent of the median income, adjusted for family size, in the county where the tenants reside.
The department of commerce shall adopt rules defining county median income in accordance with the definitions promulgated by the federal department of housing and urban development.
(3) A requirement that property owners provide relocation assistance shall include the amounts of such assistance to