I usually say pass on these things and will here.
It is a 7 year old that has had it’s feet neglected and who knows what other bad care. No way to know if the bad hoof care caused the ringbone or not but I vote no on that one. More likely genetic or conformationally related…I have seen alot of bad hoof care and rehabbed a few, some with continuing issues. None developed ringbone, even the one with the “elf slippers”. And, yes, 7 is young for ringbone from any wear and tear causes like older horses develop.
Once you get ringbone, you cannot make it go back. You can do pain management, shoe/trim to alleviate any discomfort and restrict the workload. But it is there forever.
All the management costs money-and a decent work up to evaluate the true extent of the problem to decide what management is best is not worth it on a $250 horse.
Buy this one and disappoint yourself plus risk breaking your children’s hearts when they cannot use her.