Some good discussion on this topic on an appraisal blog as far as how this might develop over time.10) Higher per unit returns than what?

Take a look at BP's blog where new articles are published every day: https://www.biggerpockets.com/blog4.

https://www.biggerpockets.com/blog/dealing-with-resolutions-...Sometimes, you’ll see a question in the BiggerPockets forums about whether it’s worth doing inspections when you get a property under contract.

The City of San Jose has on their website that new addresses are required but separate meters are optional (link below).https://snapadu.com/blog/electric-panels-upgrades-power-sources-adu/https://cao-94612.s3.amazonaws.com/documents/City-of-Oakland.PGE-Joint-Information-Bulletin-METERS-FINAL.pdfhttps://www.sanjoseca.gov/business/development-services-permit-center/accessory-dwelling-units-adus/adu-faqs

Do a Google search of air conditioning blogs or news articles.

This includes blog posts on websites as well.

I hope it helps: https://www.biggerpockets.com/blog/2015-05-25-5-dominate-pro...

No personal experience here but here's a helpful reference from someone who wrote a blog about different aspects of a 2 flat remodel in Chicago Scroll to "Two-flat journal 6: How to make an all-electric house" - - speaks a little about heat pumps and cost In the HVAC section.  

We don’t know any PMCs to recommend in the area mentioned, but since selecting the wrong PMC is usually more harmful than selecting a bad tenant, you might want to read our series about “How to Screen a PMC Better than a Tenant”:https://www.biggerpockets.com/member-blogs/3094/91877-how-to-screen-a-pmc-better-than-a-tenant-part-1-services-and-processesWe recommend you get management contracts from several PMCs and compare the services they cover and, more importantly, what they each DO NOT cover.

Again, the BiggerPockets store has some books on this topic, or you can learn about it by watching podcasts, reading blogs, and interacting on the forum.