According to POR.com.....it was all for publicity.

A group of investors have offered 50 Cent and Floyd Mayweather, Jr
$5 million to settle their "alleged" differences in the ring. According to
Allhiphop.com, billionaire Alki David and partner Damon
Feldman of Celebrity Boxing offering the $5 million for a three round
celebrity boxing match.

According to David, the show would air on FilmOn.com and
BattleCam.com -- two ventures that David owns. They would fight three 2
minute rounds in head gear -- along with big celebrity boxing gloves.

• The proposed fight will go down in Las Vegas on December 14th if the two men
  accept the offer.
• Just last week, 50 and Floyd were embroiled in a Twitter beef last week --
  which 50 later admitted was a publicity stunt.
• 50 responded via Twitter, saying, "I'll fight Him dec 14th is to soon. I
  would need to get in shape. I;m 204 right now I hit that boy he will see a white
  light."