Go custom - with a codeignitor framework. You don't want an open source platform. They are way too vulnerable for hacks and limited on functionality. (You don't want plugins where various developers' work can clash and cause a ton of bugs.)
I agree with the others. If you are on a shoestring budget and feel the need to built it yourself, use Wordpress. But, maintain high security standards. There is a plethora of themes available to get you started.
It is also better to have control of your own hosting account and file structure. Avoid hosted services like squarespace if possible.
Codeignitor is great if you have the budget to hire programmers and designers. If you go this route, give me a call. One of my clients is an offshore development group that does good work for a fraction of the US costs.
All the best!