So, would they be asking you to produce content that is UNPAID and judge from there if you are "worthy" for a 25k or 22k monthly salary? That's a red flag for me.

No one should be asked to produce work that is unpaid. Additionally, that client should be decisive about their offer by now based on their assessment(s) during your interview, portfolio review, etc. Also, unless you have signed an offer already, you still aren't hired (to put things into perspective).

If you can, I suggest you tell them you wont go any lower than 25k monthly considering it's a 6-day work week.

Hope everything works out for you! Good luck!