In court, self-investment is getting the court to pay you attorney fees to defend your 'self' who is written on the indictment. Whether you win or lose, after court is over, invoice the court for your fees, plus whatever judgment fines might have come about against your 'self'. If they don't pay, take them to court over it. After all, they were the ones who asked you to represent your self.
Then, when they indict your for practicing law without a license, defend your indictment self again. Whether you win or lose, after court is over, invoice the court for your fees, plus whatever judgment fines might have come about against your self.
This could become rather circular. But you might be able to earn a good living this way.