Beckham, 39, splashed millions on the luxury mansion, proving his commitment to America's Major League Soccer, reported Daily Mirror.
The ex-England captain will now split his time between Florida and London.
His four children will continue their education in the UK and his wife Victoria will still work at her fashion range HQ in London.
"Now he has a house in Miami, things are starting to happen. David knows he has to immerse himself in the culture. He is so excited. He genuinely wants to take the game to the Americans. It could go stratospheric," a source said.