It appears President Biden will waive $10K in student debt (with an income test)

Who is going to challenge this executive order and how are they going to fund that challenge? And when? After the order is issued and in place, the loans are forgiven?

I don’t think EO are challenged very often. A new president comes in and issues a ton of EO in the first days of the presidency (often undoing EO from the previous president). Biden has already done some loan forgiveness by EO and no one has challenged them. The ‘pause’ was done by EO first by Trump and then continued a number of times by Biden.

If Biden issues the EO and someone does challenge it in court, the ‘pause’ would have to continue and that would probably cost more than the forgiveness itself as all loans would remain on pause, not just the $10k/student (plus the cost of defending the challenge).