Ask Louis M. Solomon where his fees are coming from these days, and you will get a complicated answer.

Solomon, who joined Cadwalader Wickersham & Taft earlier this year, counts corporations like Bristol-Myers Squibb and PepsiCo as part of his book of business. Yet while companies like those still are generally paying his fees, lately the source of funds is not just his clients’ corporate war chests but money they received from investors looking to take stakes in the lawsuits he files for them.