Per
https://en.wikipedia.org/wiki/Zip2> In Ashlee Vance's biography of Elon Musk, it is claimed that the Musks' father, Errol Musk, provided them with US$28,000 during this time,[4]:Ch.4 but Elon Musk later denied this.[6] He later clarified that his dad provided around 10% of US$200,000 as part of a later funding round.[7]
I feel like someone who is able to get 90% of their funding round could either convince an existing investor in the round or convince someone else to join the round. This doesn't sound like money to "start Zip2" as you claim.
Also, note that Elon had to shower at a YMCA while starting up Zip2 (https://www.cnbc.com/2018/06/19/how-elon-musk-founded-zip2-w...). Does that really sound like a "trust fund baby" to you? I feel like a lot of the myths trying to tear down Elon Musk's successes are all sourced from Ashlee Vance's book, which in turn are based on, as I understand it, interviews of Errol Musk himself (the father).