In a wide-ranging interview with a small group of reporters, managing owner Mas said the club will not get direct subsidy from MLS and that "no rules are being changed to incorporate Messi on to Inter Miami's roster."
Miami plan for Messi, who is on holiday in Rosario, to make his debut at the DRV PNK Stadium in Fort Lauderdale, Florida, against the Mexican side on July 21.
Mas said Miami are preparing for Messi's arrival, which includes work on increasing the capacity of their stadium to 22,000 by adding approximately 3,000 seats. Security for players will be enhanced both for home and away games.
"As you may recall, Argentina trained in Miami before they flew over to Doha [for 2022 World Cup], where we had an opportunity to see some of the Messi mania at our doors on an everyday basis during practice. So, we're very prepared. We've been getting ready for this," Mas told the Miami Herald.
Mas said he believes Messi's arrival will be a game changer for Major League Soccer and encouraged other owners to "seize the moment."
"I think there will always be a 'before and after Messi' when we talk about the sport in the United States," he said. "I cannot overemphasise the magnitude of this announcement. Having the world's greatest player here is something that is significant for our league, and for the football ecosystem in the United States ... Lionel Messi is coming to this country to win cups and make a difference.
"I think it's incumbent upon myself and my partners in the league, the other owners, to seize the moment."
Information from The Associated Press was used in this story.