If it costs $150,000 and the ADU rents for $750, then it's probably not worth it.Here's a guide on how to analyze a property.

where can we find places-websites to analyze areas that will provide positive cash flow?

BiggerPockets also has a calculator to analyze deals, and I highly recommend you start this as soon as possible, even if you are not ready to buy.

ADU’s are a very popular in expensive areas, and I understand they add equity value as well.

I haven't sold yet, I've been analyzing property to get a head start on the 45-day timeline of identifying the potential replacement property (and because I enjoy analyzing property). 

In our market (New Orleans) cemetery tours are very popular. 

There are a bunch of different figures associated with this decision, such as new interest rate, old interest rate, cash flow of new property etc, but I'm having a hard time getting my mind around how to analyze the decision mathematically.  

What kind of tool did you use to analyze all that?

Granted there is a cost in hiring an agent, Having someone analyze each deal with localized knowledge is worth its weight in gold.

Start by analyzing cash flow and market demand for each property to decide which one to rent out.