It really isn't (been there, done that). The hard part is to operate it. You're going to need quite a bit of hardware (figure about 10 large machines minimum to store an index of any appreciable size) and a ton of bandwidth to do the crawling. Then you're going to have to somehow get an audience large enough to earn enough money to pay for it all. Your runway will be in the 10's of millions of bucks at the size of todays internet.
