I bet they would jump on it to save the money- or simply help them with social media marketing etc.

Based on the numbers, I am willing to bet this is located in 38126, 38106 or 38112.

Working with vetted, trustworthy borrowers and maintaining a robust vetting process will help ensure your capital works as hard as you do!

If you're looking for appraisal value an ADU may not be the best bet, but if you intend to sell, my anecdotal evidence suggests in dense highly desirable neighborhoods, ADU square footage will gross the same as the main house.

Philly is your best bet. 

Find a knowledgeable and trustworthy broker in your market that can shop amongst the various providers and find you the best deal while still making sure you have the protection you need.

While BP has a rent estimator as does rentometer.com (both allow a few free uses, I believe), I agree with @Zachary Deal that your best bet is to seek out guidance from either the listing agent or a property manager well-versed with the area. 

So Real estate is the best bet? 

Add 100 chargers to a 300 unit property and I bet there's no way the transformers and electrical infrastructure at the property can handle that. 

Working with and building a trustworthy team is of utmost importance.