Very glad to see you're interested in the RP forum. However, by forum rules, you need to have been an avid participant in one of the established RPs before setting up your own. Added to this, it might be a good idea to pitch your idea in the RP Brainstorming thread to see if there's sufficient interest. As a final point, it'd be best to flesh out your idea (such as in the other active RP threads) before posting an RP.
"Life is just a chance to grow a soul" - A. Powell Davies
Actually, no, they're not all "teen stuff". And as for the rules, it's for the well-being of the forum itself, because in the past, there have been people posting roleplays left right and center, and ended up abandoning them within a week. It gets messy, and is unfair towards the players, many of whom tend to be quite dedicated.
I appreciate that it can be frustrating to not find something you're interested in; but even if you don't feel you know enough to participate in any of the current RPs yet, you'll learn a huge amount if you just follow them from a distance for a while - get a feel of how they work, what kinds of settings and stories tend to work well, etc first; and maybe try a closed RP first (since those don't require previous RPing activity). As tempting as it always is to jump in the deep end and hold your breath, you'll probably have a lot more fun if you ease yourself into the idea gently.
Since this thread isn't a particularly strong base for an RP, thread locked. RPing is like driving - you can't sit behind the wheel of a lorry straight off the bat.
"On the page, punctuation performs its grammatical function, but in the mind of the reader it does more than that. It tells the reader how to hum the tune." - Lynn Truss, Eats, Shoots and Leaves