Harvard tuition is really not much when you compare it to other private universities. The tuition at Havard is $36k Harvard College Admissions � Financial Aid: Cost of Attendance which compares well with 2nd tier universities that charge $34k. As for the living expenses, there actually cheaper than let's say Undergraduate Tuition & Fees - College at Florham :: Fairleigh Dickinson University
The big advantage that Zuckerberg had was that his parents had the money to prepare him for Haravard:
To keep up with Mark's burgeoning interest in computers, his parents hired private computer tutor
Zuckerberg later studied at Phillips Exeter Academy, an exclusive preparatory school in New Hampshire
I think at some point he would have needed to bring in Venture Capitalists. The .com companies burn through a lot of cash and the real money isn't made until the IPO. Though, he should have started with some of his own money. At least the first 50k. I don't think that he needed to take 40k from Eduardo Saverin.
This is a quote form the article. Zuckerburg and his family knew he had something. It's not everyone that has AOL and Microsoft knocking on their doors.While still in high school, he created an early version of the music software Pandora, which he called Synapse. Several companies—including AOL and Microsoft—expressed an interest in buying the software, and hiring the teenager before graduation. He declined the offers.
This is an interesting article that I found How to Find Willing Investors | Inc.com