It's always a good idea to keep control over the rights to a song you wrote. A famous case is Dolly Parton's "I Will Always Love You." Elvis Presley wanted to record the song in 1974, but Colonel Tom Parker demanded that Elvis get half the publishing rights, and Dolly said no. Eighteen years later, Whitney Houston sang the song and made Dolly "enough money to buy Graceland." But it doesn't always turn out so well.
The song "Without You" went to number #1 when Harry Nilsson released it from his album Nilsson Schmilsson in 1971. Mariah Carey's version in 1994 became a global hit. What you might not know is that the song was written by Pete Ham and Tom Evans for their band Badfinger. They recorded for the 1970 album No Dice, but it was never released as a single. The songwriters were thrilled when Nilsson's cover became a hit. Surely they would enjoy royalties from the song, but it was not to be. Ham committed suicide by hanging in 1975, after their business manager ran off with the band's money. Evans did the same in 1983, after an argument over the royalties to "Without You."
You can hear Badfinger's original recording of "Without You," along with five other songs that became big hits in cover versions, but not for their obscure original rock recordings, at Cracked.