Starter cold crash time

If I make a 2 L starter and stick it in the fridge after high krausen to settle the yeast, how long should I wait? Would enough yeast settle after a day, or does it need to wait longer.

It depends on the yeast. Some settling will happen for all strains in 24 hours. Highly flocculant strains will have largely settled out in that period, others may take longer...if the wort is still pretty cloudy, give it a little more time (if you have it!). If I'm pressed for time, instead of dumping all of the less flocculant (and more attenuative) yeast out with the spent wort, I'll dump half or so of the spent wort, thereby saving some of the suspended buggers for the job.