Not to mention that I've also learned having two ADU's is a no-go for many conventional bank lenders. 

I am currently trying to learn as much as possible by reading books and listening to podcasts.

There's enough to learn when you're starting out, keep it simple.

Lessons learned?

First pro is you learn how to be a landlord and to manage properties and this is the best way to get started into real estate investing.

It sounds like a big misunderstanding and I guess the learning lesson is for you to always to get an invoice from anyone doing work.  

I'm sure we can learn from each other so let's stay in touch!

I am curious to learn from others as well  :)

Recommend exploring as many sources as possible to get referrals AND cross-reference them to get as much accurate information as possible.Check out NARPM.com, BP’s Property Manager Finder (BiggerPockets: The Real Estate Investing Social Network), etc.Also, encourage you to learn from the mistakes of others - by reading posts here on BiggerPockets about owners not having their expectations met by their current Property Management Company.

If you have a great investor agent, he'll be able to help with finding you personalized deals, helping you learn good/bad neighborhoods, estimating renovations/scope of work, setting you up with his team, etc.3.