The sale is subject to approval from the league's owners before it can be finalized.
Tuesday's scheduled NBA Board of Governors meeting has been canceled. Shelly Sterling had pushed to negotiate a sale before the meeting, at which both of the Sterlings' ownership interests could have been terminated.
As part of the sale agreement, Shelly Sterling and the Sterling family trust have agreed not to sue the NBA and to absolve the league of litigation by others, including Donald Sterling. There also is language in the agreement that states Ballmer will not move the team from Los Angeles, according to a source with knowledge of the deal.
Shelly's husband, Donald, filed a against the league earlier Friday.
Donald Sterling's attorney, Max Blecher, said he needed to review all the new information before proceeding.
"We gotta sit down and see how all of this affects us," Blecher told ESPN.com's Ramona Shelburne. "We have to think through the whole situation.
"[Shelly's] saying, 'If you sue us, we'll have to pay out of our own money.' It's like suing themselves. We have to see whether the law allows that to happen."
The $2 billion price tag is the most by far for an NBA team, topping the $550 million paid for the Milwaukee Bucks earlier this year, and ranks among the highest ever for a North American professional sports franchise. Ballmer defended the amount of his bid in an interview with the Los Angeles Times on Friday, saying he would be paying, in part, for the Clippers' potential value.
"I've got big dreams for the team," he told the Times. "I'd love to win a championship. I'd love the Clippers to be the most dynamic, vibrant team and name in professional sports."
Ballmer added: "The only way any of this makes sense -- my desire to spend time in Los Angeles, this team, its aspirations, this community, this purchase price, any of that -- is to really live out the dream and make this kind of America's team."
Ballmer also confirmed to the Times that another part of the sale agreement was to recognize Shelly Sterling with a sort of "owner-emeritus" status, which would make her welcome at Clippers games. Her husband, on the other hand, was given a lifetime ban from the NBA, in addition to a $2.5 million fine, and is not permitted to attend games.
Rom Klempner, the acting director of the National Basketball Players Association, lauded Ballmer in a 467-word letter to players about the sale, which was obtained by ESPN.com's Marc Stein, and said, "If the transaction is consummated, it will represent a very positive step toward ending a very unfortunate time for our league."
"As opposed to an owner who notoriously invested little in his team over the years, the proposed new owner is one who, based on his pedigree, history and the investment he already has pledged to make in the franchise, should be an innovator and a contributor," Klempner wrote. "Not just in terms of his approach to players, but generally in the manner in which he is expected to market the team and the product."
Klempner said the sale illustrated the "superb" economic condition of the league and how the union was "proud to have stood together as players against the divisive language and actions that led to this situation."