I emailed hmda help asking them if the refinance of a bed and breakfast where the borrower also lives in the bed and breakfast (1-4 house with 4 bedrooms 2 bathrooms) would be reportable. The following is how they responded:

A refinance is any dwelling-secured loan used to replace and satisfy an existing dwelling-secured loan.

Refinancing. A refinancing is any dwelling-secured loan that replaces and satisfies another dwelling-secured loan to the same borrower. The purpose of the loan being refinanced is not relevant to determining whether the new loan is a refinancing for HMDA purposes. Nor is the borrower’s intended use of any additional cash borrowed relevant to determining whether the loan is a refinancing, though the borrower’s intended use of the funds could make the transaction a home improvement loan or a home purchase loan.
It does not matter what the property type is when it comes to reporting a HMDA-reportable refinance.
Thank you for using HMDA HELP!

The sentence in blue is what is throwing me off. I always thought it mattered very much what the property type is. It has to be a dwelling of some type, correct? A refinance secured by a commercial building would not be hmda reportable, would it?

If you're refinancing a mixed-use property, then the results of the mixed-use test are what tell you whether you have a HMDA reportable refinance. If you're refinancing a loan secured by multiple properties even one of which is a dwelling, it's a reportable refinance. Your scenario sounds like a mixed-use property where the business purpose part (1 bedroom being lived in by the borrower versus 3 being used for transitory dwellings??) would outweigh the consumer part. Just my interpretation.