He also asks me to send the check in mail and then he will send the lien waiver in mail after the amount is cleared in the bank. what is the regular practice to get lien waivers from the GC's? 

I'm looking for some practical advice from other California land lords.

I made 2 simultaneous offers.

I like physical work, I like creative or restorative processes, and I love learning new and super practical skills.

Networking is always a great practice and you never know who you might meet there and what good information they have to share.

@Benjamin LovingerI have been successful on this for both directions (listings and purchases) and I find that posing the options simultaneously in an unbiased light is the best way.

For correspondent lenders, it is common practice to establish a seasoning period of around 6 months to avoid scenarios like the ones I describe above.There are a number of factors at play, but hopefully that helps explain a few reasons why your lender might require a seasoning period while others might not.

Or is it required or general practice to give access to individual units only, and lock each key in its own combination locked lockbox or closets?

You need to combine that with either DM, cold-calling, or door-knocking.Do you have any practice in listening for distress and motivation? 

Nothing stopping you from developing the skills and understanding for paper savings, habit-forming behavior to position you for a deal in the near or far future -- all of this would be good life skills to learn and practice while you are under your analysis paralysis.