I think everyone is coming on this from the wrong angle... partially atleast. The first thing he should be worrying about is if he has the funds and the programming skills to start such a site. The idea, like said, is very broad. Most social networks nowadays start with one of 2 things. Funding, or a Niche.
But like I was saying, if you are not using any prebuilt software, what are you going to use. PHP / MySql?
Are you going to prepare for scaling IF it becomes popular so that you won't have to deal with the mess of scaling a already functional website. Are you going to use a framework or write raw code. Which framework if so? Where are the servers going to be. Are you going to start off on one server (httpd, mysqld, and php all on one server) or run the services across multiple servers. ETC... ETC... ETC...
Basically what I am coming at here, is there a plan besides posting on a forum grabbing ideas of people will join.
I see where you are coming from, you want to see if people would join. The issue is that you are putting the cart in front of the horse. Are you going to be able to do it. BTW, I wouldn't expect to host a social network (even if custom coded) on a CPanel server (or any other control panel). Some hosts might be restrictive about this, so they might not like that (check TOS). So now... I come to my recommendations.
Think about the idea, take some time, an idea doesn't come over night like in the movies. (maybe rarely).
Think if it is possible
Learn a language such as PHP, Ruby or Python.
Learn how to use Linux and services such as Apache and Mysql.
So now my main comment after my rant.
You say it is like Twitter, but different in a sense. You say that the website is about people posting ideas. but... isn't Twitter about posting ideas. Even if twitter is about posting status updates, ideas, and other types of information, it still isn't going to work. As long as websites like Facebook and Twitter are partially related to your content type, I don't see anyone switching nor people joining when they could join a much busier and active place like Facebook and Twitter.
Regardless, if you wish to through with this, I wish you the best of luck