If I own multiple properties and refinance from each and put the money to buy another property while accumulating positive cash flow from rental properties, I think I can increase the velocity as high as brrrr.

Are you in a situation where capital is more critical, or are you trying to accumulate doors?

More than likely, for the first few years I may manage this property myself anyways, down the line as I accumulate more investment properties, I'll let a management company take over.) 

I'm looking to flipping houses while also accumulating a few rental properties to create a steady cash flow.  

What is your debt accumulation over that period, just $100 of your debt?

The key to growth is to maximize your leverage and accumulate as much assets as you can with the least money you can but that's a complete different topic.Here's the deal :1) Pay off your loan, get a 4% return (estimated interest rates) and that's it.OR2) Buy another rental property, get anything from 8-30% return but you have to deal with the management of it.Hope this helped you.Kevin

The longer your stay here, the more you end up losing, and more important...you have lost time that you can't recover...like you can the lost cash you've accumulated thus far. 

We would be using the equity from our primary residence in the Bay Area that had accumulated equity thanks to the red hot market here.

Equity accumulation through principle reduction. 

The 4plex would be perhaps the largest and most valuable property we could get other people to pay for in effect.We are leaning towards the 4plex, but also considering the extra cash it would tie up and if that cash put elsewhere could more than make up for the higher monthly payment , lower equity accumulation, lower tax savings of the duplex.