Age of site itself is a relatively minor factor, if at all. What does matter, however, is site authority. Authority takes time to build and you will be disadvantaged against sites that have been building their own authority. If you aggressively pursue web marketing it can take anywhere from 6 months to a year or two to be in a relatively competitive position. That all depends on the competition. If your start up is in a relatively noncompetitive field, it won't take much time at all.