Feasibility studies, demographic studies are the beginning point to understanding the demand, market product type, and pricing to assess if your desired project is feasible.  

They will charge you about $300 to $500 for an assessment and if it does qualify for more: adu or second unit, then they will of course charge you more to put everything together.

A search on the State’s Taxation and Assessments website can show the Owner of the Address and Mailing Address.

Go to the property taxes line to see what was assessed to the seller. 

@Ramsey Rimkeit are you looking at the assessed value or the actual tax payments? 

So, lower upfront fees but they will apply a special assessment to pay off the loan. 

How do I assess whether this would be a profitable deal worth investing in?

I would assess the businesses on the 1st floor, have they been good tenants and for how long.

In my area, a property assessed at $500k might have taxes of $20,000 a year.

@Felix Torres A phase 1  is a "historical" environmental site assessment that is conducted to detect any potential or existing contamination issues within the earth based upon the past uses of the property.