Comparing a Triplex to an SFR + ADU + ADU

[J Grant]

An investor would probable look in another neighborhood for 2-4. I don't have those issues, so go 5 miles. Multi don't follow the same single family rules. Since they normally represent a very small % of the market, there may not be an abundance of data, or any data. Just state there were no listings in the subject's neighborhood, went further into the subject's marketing area.
2-4 and condo are not my favorite ones to do. I normally would say there were no comparable listings within X miles. Let them come back, but mine have never come back.

It is true - a buyer for an income property is often more open to buying in a wider area range since rental income is the income they are after and typically a small income property buyer is not going to live in the area. The OP limited their search to 3 miles. IDK what is appropriate for the area but a search 10 miles but be reasonable in certain cases. As is comparing another property type, such as SFR with 2 ADUs. I tend to use a different property type as a fourth comp or in desperation cases , and as a pending, it might do.