I would say the school matters if you want to network a little and have the teacher as a resource but you already have the BP community.

I want to get more doors, my goal is 20 units and I only have 4, my thoughts are that if I dump all money and resources of financing into one renovation and cosmetics...I will never buy more buildings and get to my goal.

A great resource i is the local BP meetup that usually happens the 3rd or 4th Tuesday of the month.

Net operating income includes rents collected minus expenses.

The standard 10% usually covers tenant management only - advertising, screening tenants, preparing leases and renewals, fielding phone calls from tenants, collecting rent and conducting evictions.  

Just connect with resources in the area (ie title, escrow, attorneys, wholesalers, investors, agents) and work together with them.

another reason to move to a service like cozy.co for rent collection; both sides can see/print/etc rental payment historyOtherwise, like others noted, it should take under 3 minutes to type/sign/send via email a receipt. 

You have found the absolute best resource on the internet to learn about investing in real estate.

In the past I have sent rental contracts to a potential renter who was stationed in Korea, did a walk through of the property via FB messenger video chat, ran background checks with TransUnions Smart move, collected security deposit via PayPal and emailed the tenant the code to the lock box that had the key.

Before anyone considers that, please read CA Civil Code 2945.45 which requires you to register with the CA DOJ before taking any action as a foreclosure consultant, which specifically includes collecting overages.