I  want  to know that investment banks can provide  "non-conforming"
real estate mortgage loans so that I  shall be able to apply to the
investment  banks for that mentioned mortgage loan??  For example 
Credit Suisse First Boston international investment bank  or 
www.csfb.com  organization.

Your best bet is an independent broker whom you trust.  Most lenders
deal directly only with their brokers, who then deal with you.  It is
not worth the trouble to deal with individuals.  The broker gets the
wholesale rate because he does many loans and handles the small
hassles that go with each one.  He makes this "spread" between the two
rates plus whatever he charges in points and origination fees, some of
which are often cleverly disguised on the good faith estimate. 
Sometimes large lenders will have their own retail outlets, but the
rates are still retail, not wholesale.

A mortgage broker who is registered with many lenders can help you. 
also, imho, lendingtree.com is not horrible.  It does a similar
service as a broker.  Best wishes.