You should not think about it but you should calculate it. this is how you make money  in residential:( cash flow + appreciation + equity building ) - (mortgage+PITI) if you do not cash flow is ok as long as appreciation rate is high. 

Again, if you are financing the rehab costs then this question becomes highly critical.There is good money to be made in expensive neighborhoods and also in low-cost neighborhoods. 

U hit all the high points..

I've also added a spreadsheet for me to help me with a little extra organization.Anyway, I highly recommend it as it's easily a net positive and takes almost no time. 

One of the biggest complaints with DSTs is the high cost/fees associated with them.

If this was your primary residence, I would highly recommend selling within 3 years of converting to a rental to maintain the section 121 tax free gain on sale of a primary residence (250k exclusion for single and 500k married). 

Once you get above a SF, the properties aren't usually submetered for water.

But $40k is way, way too high a price.

It may look like a cheap 3-4 unit, but if it is in a place that is known for high turnover or other issues, then it may not be worth it.

This may be able to work if the ADUs can be added at a low enough cost that the NOI and cap rate provides a value high enough to justify the effort and risk.