Think how would you make any money off a search engine vs. the high costs of running it (i.e. big hosting needed)? Look at the competition, do you think you could keep up with the tough competition out there that of Yahoo, Google, Alta Vista, etc. etc.??
Would you pay people for searching (as in would you have affiliates that would look for people to click), how would you pay those people? Where would you allow your search engine to be advertised? Would you allow affiliates to ask others to search, or would you just have a set of rules that they could not beg for searches?