(SFH vs MFH, size, lot, etc...)  

If it means that you're not very good at conceptualizing what needs to be done, and how much it costs, you should have someone good assist you/do it for you, even if it means hiring someone (depending on the size of your business), because getting the math wrong will mean the difference between success and bankruptcy, and this is even more true the further down the ladder you go in terms of profit margins. 

And if what @Jim Costa wrote is true: "Instead of a refinance you can get a HELOC and pull out 90+%", perhaps that WOULD net you a greater portion of its equity into your wallet?

It has a small 2nd structure on the property that used to be a 2nd garage that someone finished off and now is living area ( am not sure the exact size but I am looking into it.  

Since my goal was both equity and cash flow and I was new to this I instantly jumped into the Equity portion rather than letting the effects of the rehab on the property and financing build equity over time and this has hindered my growth in number of properties because I spent way too much Capital per $1 of cash flow.So, how much capital did I spend per dollar of cash flow to get a single dollar of cash flow?

Of course every year we will probably add to the pot but again I want to think it will supplement a smaller portion, maybe guessing 10k more or less every year.  

.- Sewer sizing.

You ask about>50 units... is that the size?

You're going to need some type of written documentation to protect your portion of the investment, ie the rehab expenses.  

Could there be an issue of the shear lot size to where it couldn't be built on anymore or for a mobile to be placed on it dude to law changes?