My name is XXXXX XXXXX I'd be happy to answer your questions today.
Unfortunately, there is no law that dictates how much a landlord may raise rent. Provided that he gives the appropriate amount of notice, a landlord may raise the rent to any amount that the tenant is willing to pay. A tenant who is not willing to pay the stated increase has a right to choose to terminate the tenancy and move.
Here is what the statute says (the bold is in the statute, the italics are my emphasis): 90.600 Increases in rent; notice; meeting with tenants; effect of failure to meet.
(1) If a rental agreement is a month-to-month tenancy to which ORS 90.505 to 90.840 apply, the landlord may not increase the rent unless the landlord gives notice in writing to each affected tenant at least 90 days prior
to the effective date of the rent increase specifying the amount of the increase, the amount of the new rent and the date on which the increase becomes effective.
(2) This section does not create a right to increase rent that does not otherwise exist.
(3) This section does not require a landlord to compromise, justify or reduce a rent increase that the landlord otherwise is entitled to impose.
(4) Neither ORS 90.510 (1), requiring a landlord to provide a statement of policy, nor ORS 90.510 (4), requiring a landlord to provide a written rental agreement, create a basis for tenant challenge of a rent increase, judicially or otherwise.
If a tenant has a set lease agreement, the tenant may not increase the rent at all during the term of the lease, but there is no limit on increases when negotiating a new lease.
There is one exception - if a landlord increases the rent within one year of converting to condominiums, the tenant may be entitled to damages. I don't have enough information to know if that would apply to you.
You may also want to check with the city to see if there are any rent control ordinances available in your area, since there is no statewide law.
I apologize that this was probably not the Answer you were hoping to receive. However, it would be unfair to you and unprofessional of me were I to provide you with anything less than truthful and honest information. I hope you understand.