LAS VEGAS — Floyd Mayweather Jr. is enough of a businessman to know his latest fight would be a tough sell, especially after setting records with Canelo Alvarez his last time out. But sell he must, even though oddsmakers and nearly everyone else give Marcos Maidana little chance in their welterweight title fight Saturday night. A full house is already guaranteed at the MGM Grand hotel arena, but Mayweather needs people at home to pay $64.95 for the fight if he is going to recoup his guaranteed $32 million purse.