You should have a contact agency who is monitoring the rents. I have 8 different apartment buildings, one duplex. I usually have to send them reminders to file their rent rolls. I use whatever classification they normally would be and then I adjust the value with an override to get the max 8% tax. It is the only way I can do it with Munis. If you have Vision Admin, you can apply an exemption which is the difference in actual tax vs. the 8% max tax.
We also have quite a few “affordable” single family dwellings in new subdivisions. Vision created a new code in my construction details as “Affordable” since these have a maximum value.