So I will effectively be paying $2k/month for a 800sq foot 2bedroom/1 bathroom in National City.

Learning just how badly freeways effect your sale price in the end.

But then you effectively become landlord to a friend.Stating the obvious...your friend should start building credit history. 

What would be the most cost effective and smartest move for a rental to update the heat system?

(Pre-foreclosure, distressed, others) There has to be a method that is more effective than going to every door on every street.

We certainly have because it's counterproductive to an effective relationship.

Sounds like you already know the most effective ways of digging up those off-market deals. 2) Everyone has their own ROI goals and metrics. 

I'm not saying this to toot my own horn but I personally found self-teaching to be more effective in exercising a desire and passion to learn.

I can tell you that at least on a monthly basis we get a deal from driving for dollars whether it is FSBOs, For Rent Signs, seeing move out trucks and I barely do it anymore because it's my least effective strategy. 

Effective July 1, 2017, the annual allowable rent increase is 3%.