Don't split it. You said:
My primary motivation is the concern that handing the whole project to a single entity opens me up to the risk of the website being cloned easily or sold on to other clients with similar projects. I guess I thought that if it separated into to two components one isn't of much use without the other so, isn't much of a threat(competition-wise) if stolen. Like I said this is my first project, so I'm already learning that maybe doing things this way isn't standard nor advised.
It doesn't matter how unique you think that new site you are creating is, there are already some of those out there. Its not only the creation of the site that you need to be concerned with, but also how you will promote the service and any additional value that's beyond the site that you might add with your service.
If the project is as good as you think it is, other people will clone it anyway - and if they are experienced it will cost them a lot less than any 'random' team u pick ... they will do so, without the source. Its beyond the site, is the whole service and everything that comes with the business.
Ps. find a good team, break the project into functional pieces that can be published to production before everything is complete ... a good team should help u structuring it so u see progress weekly (or bi-weekly).