I am having a need to have a database that has multiple levels of
access.
for example
level one (owner/admin) will have access to everything on the site
including creating and deleting agents.
level two (agents) will be able to browse and post products to the
site including the price at which the owner has bought the product.
level three(buyer) will be able to just browse the listings but will
not be able to see at what price the owner has bought it. but will be
able to see all the other details.
To give a bigger picture this is how it should work.

The owner has a widget for $500.00 or a seller offers the widget for
$500.00 to the owner.This data is entered in the database.

The prospective buyer searches the site. he finds this interesting. he
contacts an agent listed on the site.

now the agent will take that request and search the site for details
and will see that the owner is able to buy that for $500.00 and he
will do his calculations send a quote to the buyer.

I saw a couple of listings in hotscripts.com that came close. for
instance interactivetools.com - Auto Manager,Vessel seller
,OpenAutoClassifieds

but if you can give me a perfect match for my requirement or something
that can be customised to meet my requirement that would be great.