Under RCW 59.18.030(29),
"Rent" or "rental amount" means recurring and periodic charges
identified in the rental agreement for the use and occupancy of the
premises, which may include charges for utilities. Except as provided
in RCW 59.18.283(3), these terms do not include nonrecurring charges
for costs incurred due to late payment, damages, deposits, legal
costs, or other fees, including attorneys' fees.
Per RCW 59.18.283(2)
Except as provided in RCW 59.18.410, the tenant's right to possession
of the premises may not be conditioned on a tenant's payment or
satisfaction of any monetary amount other than rent.
In other words, additional regular fees are disallowed. All recurring fees must be "rent" (but things like late fees, damages, attorney's fees which arise only occasionally are allowed). If a lease were to specify $2,000 as the rent and $1,000 as the "___fee", as a recurring charge it would still be considered to be $3,000 rent. One cannot get around the 60 day notice requirement of RCW 59.18.140(3a) (which says "a landlord shall provide a minimum of sixty days' prior written notice of an increase in the amount of rent to each affected tenant, and any increase in the amount of rent may not become effective prior to the completion of the term of the rental agreement") by calling it a "continuation fee". One does not need to get around rent control because per RCW 35.21.830,
The imposition of controls on rent is of statewide significance and is
preempted by the state. No city or town of any class may enact,
maintain, or enforce ordinances or other provisions which regulate the
amount of rent to be charged for single-family or multiple-unit
residential rental structures or sites other than properties in public
ownership, under public management, or properties providing low-income
rental housing under joint public-private agreements for the financing
or provision of such low-income rental housing.