toonew2php

I wanted to ask for some advice regarding php based web programs-- B2B programs in particular. We were supposed to hire programmers to make one similar to alibaba.com, but a simpler version. While doing some research, I saw some websites selling already made ones such as http://www.softbizscripts.com... are these any good? We were thinking of getting something like this then hire a programmer(s) to customize appearances and some features. I asked around and got mixed feedback-- some said it's ok and you don't have to reinvent a wheel, while some said coding from scratch is best. My worry if we buy a pre-made one is the possibility that it might be more difficult (if not impossible) for our programmer to modify it/someone else's work. What do you think? TIA