Multi family vs. Multiple single-family units

[Wendy Huang]

1) Is it true that to invest/buy a multi-unit apartment one would need minimum 20% down payment?
If that's true, isn't that only possible for big finance companies (not for individual W2 earners, despite solid income bracket)?

2) Also, I have only seen an Apartment complex sold as an entire triplex or 6-unit etc, and never as partial sale (i.e. selling only 2 units out of a 6-unit complex, for example) so it is WAY LESS liquid in case if investment goes poorly?

Also, these Apartment complexes take WAY LONGER to sell, based on the days theystay on realtor.com, Trulia etc

3) Even though it is more time consuming (lots of offering/loan/inspection/closing deals), wouldn't it be less risky/more liquid to buy 10 cash-generating single family units instead of buying one single 10-unit complex? This way, you can sell the home that is not generating positive cash flow?