If you just need something simple, you can build it yourself. Like others have said, Wordpress is really simple and straight forward to use.
Blogger is easy but fairly terrible from a user point of view, and obviously you want people to be able to use your site!
I wouldn't recommend Weebly. It's drag and drop so easy to use, but again not so great from a user point of view - it has accessibility problems and not always compatible with the many devices out there.
If you want it to look professional, keep the theme simple. Look for a responsive theme to ensure compatibility with a variety of devices.
I would definitely recommend getting your own url rather than using yourname.wordpress.com and also self-hosting rather than using the Wordpress hosting as it is more flexible and you can add Plug-ins to get all the features you need for your site. If you only need a small site, hosting is fairly cheap. I use Catalyst2 on a couple of small sites as it's about £15 a year when you add in VAT. And they have great customer service. Their control panel has a one click installer for Wordpress so it's really easy to install it.
If you do want to hire a professional, for a simple 4 page site, if you are providing the copy and images, you're probably looking at around £1,000 for a good designer. Too cheap and you're getting rubbish quality work that might look alright now but will age quickly and will probably be badly built. Too expensive and they're pulling a number out of the air.
Most of the work is in the designs so it can often cost the same if you want 20 pages as if you want 4 - they still have to come up with a good design that reflects your brand and code up a template, adding extra pages in to that template is the easy part.
There are some good designers that specialise in small businesses and have rates and a friendly attitude to reflect. benjaminhawkyard.co.uk/ is really good and so is laurakalbag.com/
If you have any more questions, feel free to ask.