The questions @moretea; asks are the questions that you should ask yourself because, whether you do it yourself or you hire someone to do the job, are important to know the goal of the site.
Every website needs a goal, you build the whole site around that goal, something that need to be accomplished (be it getting new customers, or only visitors, sell something or saving time by providing a new channel for claims...)
In your case, it is the exchange of information: some people will introduce some data that needs to be viewed by other people.
Now, the more detail you are in the process, the better for your project. One of the things you need to know if this is going to be really complicated.
Some other questions you need to ask yourself is when you need this to be ready and you budget.
Deciding if you want to do it yourself or hire someone is hard. But if you have not time and not passion for this, the route will be hire a web developer (and a designer, if you want it to look nice)
Also, the budget is going to limit the result (most of the time, of course. As with anything in life, you sometimes can find talented people for little money but that's no the case and if you want quality, you need to pay for that)
You're likely to use a CMS (Content Management System) to speed up the process.
Of course, this means that you have a domain and a webserver to host this web page