If you build a permitted detached ADU on home with 1 SFH will it be classified as a multi unit after the build or just a single fam + ADU? 

There's no need to be pedantic about how to classify that $25,000 margin.

I don't classify any hotel as the same as a STR.The hotel owner should be able to provide the data you need.

To be classified by the IRS as a short-term rental and get the tax benefits you must meet the following requirements (defined by Treasury Regulation Sec. 1.469-1T(e)(3)(ii)(A))The average period of customer use is 7 days or lessThe average period of customer use is 30 days or less.

There are specific requirements that need to be met in order for an ADU to be legally classified from a lenders standpoint.

Classifying your areas as D+ tells me you're already trying to justify this path to yourself.

The geo report classifies it as “potentially active” and minor.

@Kelly Cruz Rentals are classified as Fixed Assets and Flips are Current or Other Current Assets depending on how you have set up your books.

Because of the uniqueness of the house and the condo regime that was in place for Unit A/B, our mortgage lender, and our appraiser were finding it difficult to classify and appraise the home.

@Bob SacamanoCode Section 280a tells us that if you stay at a property you own during the tax year amounting to the greater of:14 days, OR10% of the total days you rent it to others at a fair rental price.They will classify it as a personal residence.