I founded my zoo step by step. Twice actually, in two different countries. I did not sell my house or personal items, I'm not Richie Rich, have not won the lottery (yet?) and I have never heard of any zoo successfully established by crowd funding. I don't have 70 millions to spend, my zoo is tiny and I do most of the work by myself, but it's still a licensed zoo with over 50 animal species. I don't know how
@Westcoastperson got his / her zoo running, but you can read up on my story here:
How to found a zoo - WdG Greifswald and WdG Salzburg [Welt der Gifte Greifswald (Closed)]
In general, founding a zoo is indeed something for the affluent if you want to follow the usual path of charismatic megafauna and mass entertainment. There are, however, other ways, but none of them will make you rich. ^^