High-yield bond funds are attracting huge amounts of investor money these days. Given today's interest rate environment, this is a trend that is completely understandable -- and dangerous. With savings account interest rates near zero, and U.S. Treasury yields under 2 percent, it is only natural that investors are looking elsewhere for income. High-yield bond funds are being marketed as the answer, but before you buy a high-yield fund you should know that they represent a level of risk much higher than savings accounts or Treasury bonds. Here are four things you need to know before you invest in a high-yield fund.