Certified residential appraisers can appraise 1-4 family properties that have transaction value of less than $1,000,000. The gray area is... there's no definitive explanation of what 'transaction amount' means. Is it the sales price? The loan amount? That has never been made clear.
I've asked that of many instructors. They all said its the loan amount and that's what I went by.
Also, I rented a duplex to an organization that helps the MMH, mildly mentally handicapped, and they used it for a 'group home'. Two bedrooms each side, two individuals in each side and a full-time assistant' that hung around 24/7. They paid above market rent, slightly, because the tenants tended to break things, not out of malice.
Before anyone starts quoting zoning regulations, they need to check out the fair housing laws. I don't know if it's just this state or federal (I'm thinking federal) but this type of group home is allowed in any residential zoning; you cannot discriminate. This same organization I rented to also had several large homes in SFR neighborhoods. Of course the neighbors didn't want it but the city couldn't stop it. BTW, these types of individuals are harmless, mostly lower-IQ that had jobs at Goodwill or other companies that hired their cohort. I'm thinking there might have been a couple of appraisers on one side.
EDIT: Just found this.
Yes, group homes are generally allowed in residential areas because federal laws, like the
Fair Housing Act (FHAA), prohibit discrimination and allow group homes to operate in neighborhoods, although local zoning ordinances can impose reasonable, non-discriminatory restrictions on the size and location of these homes. State laws may also permit or regulate specific types of group homes, such as those for the mentally or developmentally disabled, as is the case in Indiana.