However, the less cash-flow the greater your reserves should be to mitigate your risk. 

At a 75% LTV purchase (standard non-owner occupied LTV) you can afford just under a $400K property with no reserves from the money extracted from your home. 

I would like to start using private money from friends and family to finance future deals so I can keep personal funds as reserves in case things go astray. 

Hitting their minimum debt-coverage ratio (typically 1.2) may be an issue.Also expect to have 6 months of reserves set aside.You don't have a loan term in your analysis, but 7% interest is high.

For example, if I was in my 20's or 30s I would be building an REI portfolio and probably leveraging more with some cash reserves and not sit on too much Equity.

The HUD FHA 203k rehab loan will sometimes allow a non-for-profit to be the borrower if it has strong reserves and financials.

Not to mention loan costs such as appraisal fees and of course reserves to service the loan payments until you can flip or rent.As to when is the best time to get to know HMLs or a broker?

@Sang NguyenYou can get a 3-4 unit with FHA and only 3.5% down. 3-4 units do require 3 months of PITI for reserves and they must be your own funds. 

You should have some reserves and a good credit score but, those are not as important as they are in conventional financing. 

Then have the reserves necessary to cover your deductible at a minimum.