Value of light-to-none peer reviewed pay-to-publish articles I have been approached by an international student about doing a PhD with me. As an MSc student in his home country he has published 3 articles in pay-to-publish venues, that are known to have little peer-review process, with his supervisor as second/senior author. These articles are not particularly good and likely would not have been publishable in more traditional venues.

I am struggling with how to evaluate these articles and the candidate. Should I simple ignore the place/type of publication and evaluate the work on its own? Can articles in pay-to-publish places really be fairly evaluated? I am worried that changing his behavior will be difficult. I don't want to accept a student whose goal is to publish things in pay-to-publish places.
From your description, it sounds like the problem is more likely to have been the MSc supervior than the student.  As evidenced by some of the questions we've seen here, it's very hard for people new to academia to figure out which venues are reputable on their own---and the advice we give usually includes talking to someone in academia.  If the supervisor's name is on the publication, that presumably means the supervisor encouraged publication in these venues.

Especially if it's a journal which does a small amount of peer review, I wouldn't assume, without further evidence, that the student has any idea that the papers weren't fully peer reviewed.  If the supervisor isn't active in the international research community, I'm not sure I'd even assume the supervisor knows that.