If you want to buy queens, you can do the split and then check the splits the next day for starts of queen cells. If the split is noisey, perhaps a bit aggressive, and there is queen cells, then they don't have a queen, you can wreck any queen cells started, and add the new queen. If they are quiet, no queen cells, then they probably have a queen already. Plus the queen is easier to find when the hives are small.
Rick