This year he'll pass the $1 Billion mark in terms of earnings. That is pre-taxes and agent fees, etc, but also before you add in investment incomes and the growth of any assets he's bought. So I have no clue what he's actually worth. Not enough to buy a whole team, but most of the time people go in together to buy teams even if they're multi billionaires, and take out some loans. He could be the principal owner or at least the managing owner if he really wanted to once his career is done and he thinks he can spend more time actively managing something. But does he really want to be the public face if it means taking blame? He seems to be the guy that wants everybody to like him, even if he should know the nature of sports means there are winners and losers, and people hate losing and therefore the people responsible for that loss. Maybe he's gotten better at that as he's gotten older, I haven't followed the non-Celtics NBA as closely as I did ten years ago.
https://www.cbssports.com/nba/news/lebron-james-will-surpass-1-billion-in-career-earnings-in-2021-per-report/
Michael Jordan owns almost all of the Charlotte Hornets, but he has his own division of Nike (a cash cow nobody else has ever gotten), he bought one of the least valuable NBA teams when the league franchise values were lower relative to other sports leagues, and as big of a marketing deal Lebron is, Jordan was enormously larger in his era. I don't know that any other ex athlete is going to be able to earn enough to own 90+% of a sports franchise in the NBA, NFL, or MLB.