I think your best approach is to pretend you are the investor yourself, calculate build cost (mortgage with interest) + Maint / cap expenses/ management fees according to your zoning and then compare that to the average rent in that neighborhood.

I was working with a DSCR lender on comparing options on a seven property portfolio purchase a couple years ago and the difference between bundling them and doing them all separately was negligible.

But I guess, compared to a lot of new people, I take the stance of: those that are truly successful in whatever business they are teaching don't have time to teach.  

Compare comps of recently sold homes in the last 6 months ( In this case, where do you find sale information?

If you are comparing the two, you may get more appreciation, but more issues in Long Beach versus something steadier in Riverside.

I am comparing both of them right now and while people seem to prefer Propstream, I am surprised to see how many comps do not come up in the search, while Batchleads and even Zillow give me more results (using the exact same filters).

So, that example is not relevant/comparable.

Days on market is about 2 months, slightly better than earlier this year but relatively speaking, it's still a more balanced market compared to rest of the Bay Area.

I will say that some of the listing prices and projected rents seem high when comparing against my own research.

However as you correctly point out this is far more risky and or its risk capital compared to buying a income property.. but the reward can be strati-spherically higher .. not just a little bit but it can be life changing profits on some of these deals.