Want to build Real Estate Portfolio; Where to Start

[Gash Nag]

Couple of my friends and I are looking to start investing in multi-family apartments. All of us are with regular day time jobs and have less time to manage.
Scenario I envision is: Pool up some money and buy few properties  and Identify property managers to manage them. My friends and I will be retiring in next 15 years and so our plan is to own atleast 50 units by then so that we can make approximately 25K  per month. 

How do I start? I am trying to find out how do we even start? First identify a team of good RE agent; We need RE agent that can help get deals; But question is: Which markets? We are open to have in SO California preferably, but willing anywhere ; So how do I get RE agents in different markets?

Then, Some of them in team want to get lawyers opinions on any liability issues that may come up from renters. We will also need a financial company to provide us loan. 

I am sure similar questions may have been asked umpteen times but could locate the thread. Please point me to any resources.