He does not appear to have any money of his own and I do not know if one can sue future earnings. I don't think that there will be any lawsuits of that sort since there would be no money for the lawyers.
Given that he has an acquittal, and the massive amount of evidence supporting him, it is unlikely that anyone would be able to win a lawsuit against him.
Is the pedophile who threatened to kill him and then attacked him going to be a winnable civil suit?
Or the domestic abuser who strangles women, who took it on himself to attack Kyle twice, while Kyle was running to the police, with a deadly weapon going to be it?
Or the burglar who said on stand that he was afraid for Kyle's life and that he wasn't shot until he had pointed a gun at Kyle's head?
No. None of them have a case.
However, I expect a flurry of lawsuits
by Rittenhouse soon for the blatant and correctable lies several media outlets produced and are still producing. He won't have as easy a case as Sandmann, but it's possible he ultimately walks away with 9 figures just the same.