Bill Gross believes MLPs are really attractive right now.Bill Gross made a lot of money for his investors (and himself) at PIMCO, the investment management firm he co-founded. Forbes estimates his net worth at $1.7 billion. He made most of his money investing in bonds (he's known as the "Bond King").Today, Gross favors a different type of income-generating investment: master limited partnerships (MLPs). Here's a look at why he prefers them over other pipeline stocks for those seeking tax-advantaged income. ...