Well I just had a question in mind that a wealthy investor invest his money in any IPO before it goes public.Said that I am referring through recent Goldman Sachs and Facebook deal worth $450 Million at a valuation of $50 Billion dollars.

1.I want to know what is its procedure and how are these valuations made prior the company goes public.

2.Is is possible that a investor raise capital from investment banks,private equity or commercial banks to invest in pre-IPO at some valuation.Knowing that angel investors doesn't provide so much money,can they play their role here with a normal investor?

Note-I am not a wealthy investor nor a HNWI,I just had a question in my mind.