We will only be starting with about 20k-30k and we had originally planned to start flipping houses to build capital quickly, then build our rental portfolio to create stable passive income, and then build other tiers. 

You can find both with a quick google search.

He needs to cash out quickly but is willing to lower the price to 500K if he can still manage them ( manages about 30 units in that area).

As you can see, all those cost savings that people keep telling you about quickly evaporate.

If you plan to live in it for an extended period of time, and you can comfortably afford the monthly payments and all associated bills then it shouldn't be an issue.

I haven't got the PM involved with the underwriting as I try to do a quick analysis to see if it works before I dive into the details.

I did a couple long term live-in "flips", but nothing at a quick pace (hence first "serious" deal).

Pull the listing and you can relist after a certain period of time.

I'm starting to analyze one deal per day for practice.Is there a quick way to calculate rehab cost and ARV (without overthinking it) before making a thorough analysis of property?

The opportunity for investors to purchase a desirable property quickly is a major reason to seek private lending.