I don't see how this question is answerable based upon the limited amount of information provided. If by "young" the individual means 18, then I would say put all of your investment dollars in growth. If "young" means 25, I would begin to diversify a bit. 10% into a high yield bond fund is not a bad idea.
The comment about buying when it drops is a useless suggestion. Dollar cost average. Market timing is a fool's game for the most part.
Prior to investing one penny in any equity or fixed income vehicle, I strongly suggest reading Naomi Klein's, Shock Doctrine: Disaster Capitalism. Apply the working principles presented to the upcoming FED meeting and to the recent barrage of news relating to the homebuilders and the banks and the resulting dip in the high yield universe. If your analysis determines that a second buying opportunity in this cycle is at hand, act accordingly.
Concur with af25421197. Most young (under about 50) folks would likely be much better off in growth funds. Would also look strongly at international funds. Go to the Vanguard, and other no-load family, web sites and look at the 1, 3, 5 year returns / charts.