In the Netherlands (especially in the larger cities) affordable housing for people with lower income is limited. Houses to rent within a certain price (the liberated sector boundary) are reserved for people who have a relationship with the region, for example if you work there, you already live there for two consecutive years or if you were born there.
For this type of housing your income must not be too high in relation to the rent. The housing permit is issued only if the relationship between rent and income is in accordance with the requirements of the housing allowance.
If you are going to rent a house with a rent price below the liberated sector boundary, some municipalities require you to have a housing permit.
For up-to-date information please refer to the website of your local council.