The company of Scott Boras, baseball’s pre-eminent agent, provided tens of thousands of dollars in loans and payments to the families of poor Dominican teenage prospects, according to people with ties to Mr. Boras, raising questions about whether the company exploited the prospects and violated the rules of the Major League Baseball Players Association.

The union, which oversees agents and restricts many such transactions because they create a financial tether that can lead to the player’s becoming indentured, can levy penalties ranging from a fine to revoking an agent’s right to represent players, sports law experts said.

“The money obligates them to the agent, gives the agent leverage, and coerces the athlete to do what the agent wants because of fear of foreclosure or other adverse consequences for the athlete or the athlete’s family,” said Mark S. Levinstein, a prominent sports lawyer who is a partner at the Washington law firm Williams & Connolly.

According to the union’s regulations governing agents, loans of more than $500 a year to players and their families are prohibited unless the purpose of the loan is disclosed to the union.