Most of the large format enlargers will do 24x24 on the baseboard, and most of the medium format enlargers have reversable heads that allow you to place weights on the baseboard and then project to a lower table or the floor.

24" prints are a real challenge for someone with considerable experience in the darkroom. For someone brand new to the dark arts, it may be overwhelming. Just getting trays that large will be expensive, not to mention paper. You'll quickly learn just how much paper goes straight from the fixer and into the trash!

The fact is, very little of anyone's work is worth a 24" print, at least on the first go around. It's much more practical to make 11x14 prints, live with them for a while, see what sticks with you and becomes part of a larger body of work, and then make big prints.