Attorney Thomas Van Flein filed a motion seeking permission to conduct out-of-state depositions and obtain financial records from the magazine, CNN, Entertainment Tonight, Vanity Fair, the National Enquirer, Star magazine and Insider.
It could take a judge weeks to decide on the request by Palin, the teenage daughter of former Alaska Gov. Sarah Palin, the 2008 Republican vice presidential candidate.
Van Flein told The Associated Press on Thursday he didn't expect any First Amendment issues with the request of the media companies.
"At this point, we do not expect a legal battle with any of the entities we are trying to subpoena since we're not looking for confidential source information," he said. "We're merely looking for payment information."
Johnston, 19, has said he wasn't paid for many of the interviews. His attorney, Rex Butler, didn't immediately return a call Thursday seeking comment.
It's the latest twist in the ongoing drama between Johnston and Palin after the birth of their son, Tripp, in December 2008. The pregnancy was announced three days after Sarah Palin was introduced as John McCain's running mate.
The unmarried couple broke up after their son's birth, with much of the subsequent wrangling playing out in the media.
Van Flein said the Wednesday filing is routine as they try to determine Johnston's income.
Johnston, who has posed nude for Playgirl for both online and print publications, also hopes to land acting jobs.
In court documents filed earlier, Johnston said he made $101,000 last year, but notes that income in the entertainment field can be erratic. A previous estimate of his income was $105,000.
Palin is seeking $1,688 a month in child support, down from an initial request of $1,750 after Johnston's income was adjusted. She's also asking for retroactive payments to the boy's birth, or $19,232 total. That does not include $4,400 Johnston has already paid in child support.
