Hi Anthony!
I'm relatively new to the investing world myself, but from everything I've heard and read, Cash is king.
If you put down the least possible amount, yes it will bring in less cash flow for that specific unit, but it will leave you with more capital to invest in other units, which will give you more cash flow in the end.
I'll steal the example from the BP UBG - if you've got $100,000 and buy 1 $100,000 property that produces $1,000 a month, that equates to 12% return on investment annually.
If you take that $100,000 and use it to put 20% down on 5 similar homes, giving you $80,000 mortgages on each home, you'd cashflow about $300 per unit, which equals $1,500, or 18,000 per year. which is an 18% ROI annually.
Bottom line again, Cash is King. If you can put 20% down and it still cash flows well, go for it, if you have to put 30% down for it to cash flow, maybe hold off and run some numbers again.
One thing I've learned is the numbers are never as good as you think they're going to be.