When early in their careers, many actresses or models have to do things that in later years they would not do. In order to get food or pay the rent, models often choose to appear in questionable films or photo shoots just for a few bucks to hold them over until the next opportunity comes along. The wife of professional loser Rick Jones, Marlo appeared in an adult film, as did Superman. The She-Hulk appeared, albiet unwillingly, in the pages of an adult magazine.
Marvel's permanent has-been-that-never-was model/actress/party-favor Mary Jane Watson is another fame-seeker who paid the bills by supplementing her income with whatever modeling job was available. In Fantastic Four v1 #120 (March 1972) Mary Jane looks to be the featured model of Pin-Up Parade, the sleazy girlie-mag held in Ben Grimm's paws. The magazine looks like one of those that has a disclaimer on every page that claims "All models are at least 18 years of age. Proof of Age is on permanent file at the main offices at 666 Rockefeller Plaza.".
Someday, I expect Mary Jane's past will return to destroy her just as it did to Karen Page.
FYI, if you have never read Fantastic Four v1 from issue #1 through #200 (including Annuals), you really should at the earliest opportunity.