If they are asking outside the context of a language exchange and are requesting monetary compensation, then yes, I'd say that is wrong. Unless they are officially a teacher/tutor on the Italki platform, then their actions are inappropriate. I'm not sure whether it is against the rules or not, but it probably is. 

It's not allowed of course, but italki is currently not accepting new community teachers for Spanish and they don't communicate this very well. There are lots of people who want to become teachers and don't know how to go about it or whether or not it's even possible.

At this link you can find the list of which teachers they are accepting applications for. So for Spanish, they are currently only allowing professional teachers.

https://support.italki.com/hc/en-us/articles/115001499873-Which-languages-are-open-for-applications-

Offering teaching services outside the platform is wrong because this may impact the participation of users here. 

its wrong.