Your broker is earning a commission and does not have your best interest at heart. Otherwise he would NOT suggest that you invest in a fund that has not one but two major risks.
It's called a high yield fund because it invests in bonds with significant credit risk. That means the municipalities that borrowed the money may not collect enough in taxes and fees to pay the interest they owe. They could default. Another risk is that the average maturity for this fund, according to Morningstar, is 18 YEARS. This means any uptick in interest rates could make a really major dent in your investment because the value of the bonds would decline.
If your broker was suggesting this as a portion of a large portfolio it might make sense to take this kind of risk.
But you have a very specific purpose for this money and you're going to need it over a very short period of time. That means you need to concentrate on safety of principal and accept the lower interest income that comes along with safety.
Scott