COREO is a company that is specializing in such real estate services inside and outside the Pearl, such as the Zig Zag towers, etc. T the resale price is more often than not more affordable than what is being offered by the developers. You can even take a look online at:
.

http://www.mycoreo.com/property.aspx

or just

http://www.mycoreo.com/

Hope that helps :)