Floyd Mayweather-Manny Pacquiao weigh-in ticket sales to begin Fri.

Tickets for the long-awaited Floyd Mayweather-Manny Pacquiao welterweight title unification fight on May 2 at the MGM Grand in Las Vegas quickly sold out Thursday -- only about 500 were available for public sale -- but on Friday, those shut out of the arena on fight night will at least have a fighting chance to buy tickets for the May 1 weigh-in.

Tickets, priced at $10 with all of the money generated earmarked for charity, will go on sale at 3 p.m. ET Friday (with a total ticket limit of 10 per person) through the MGM Resorts call center or any MGM Resorts box office.

Weigh-ins are free to the public under Nevada law, but an exception was made for the Mayweather-Pacquiao weigh-in, which also will take place in the MGM Grand Garden Arena, because the promoters and casino wanted to avoid thousands of people camping out overnight at the MGM in order to secure a seat at the weigh-in, where it usually is first come, first served.

By making fans buy tickets, they will avoid the crowd chaos and seats will be assigned.

Pacquiao will donate his portion of the ticket sales to the Cleveland Clinic Lou Ruvo Center for Brain Health, which has a branch in Las Vegas and has done extensive studies on the brain health of boxers. Mayweather has designated his share of the ticket sales to the Susan G. Komen for the Cure foundation, a breast cancer charity the fighter has supported through the years.

"The weigh-in is always the grand finale of fight week activities," said Leonard Ellerbe, CEO of Mayweather Promotions. "And with the massive interest in this fight, the number of fans looking to attend the official weigh-in is going to be something we've never seen before. We're excited to be able to use the enthusiasm around this event to provide donations to two very deserving charities."

Said Top Rank chairman Bob Arum, Pacquiao's promoter, "The charge of $10 for the weigh-in will benefit two great charities. All proceeds will go right to them. This is a win-win situation for all."

Hundreds of thousands of fans are expected to descend on Las Vegas for fight week, with the weigh-in the final time Mayweather and Pacquiao will face off before they get in the ring the following night in the one of the most anticipated fights in history.