Second, I understand the small down payment since your buyer is going to have put some money and sweat equity into the property. 

I would say my favorite method to buy with is "sweat equity".

The real estate investors also do not factor in the years of sacrificing through losses, taxes, poor returns, and sweat.

I got in this business so I could wear sweat pants everyday.

-This is a great point though, either have to have reserves, good cash flow from a W2; or bust your *** on some sweat equity and eat Ramen for a year if you want to go zero to hero like I just did!!

And, for those people who have more time than money, they can put in sweat equity into directly owned real estate.

Don’t sweat the the threat of a lien.

Come on show some pity man, I got the shakes and sweats and I'm in need!

Put another way, how much (%) of the $30k is based upon sweat equity? 

The lack of financial equity was made up through sweat equity.