To Purchase or Pass

Hello,
I'm looking for a jumper horse for my 16-year-old daughter, who has been riding for 11 years with a trainer. We found one thats a good fit temperament wise(the horse quickly latched onto her mores than the trainer its been with for a year, and immediately began following her like a puppy-dog), however the fellow has some issues. He is a 5yr old holsteiner gelding, broken at 3, and sent to a trainers a month later. The horse has a full brother who was sent to the same trainer at the same time (he is a year or so older). The older brother was completely ruined &*soured at this trainer, and the horse i am interested in was 'salvageable' as the (new) trainer has put it. The horse does not go on the bit at the moment, and his training is more similar to that of a barely-backed 3yr old. In addition to this, as a foal, the horse had Check-Ligament surgery (which to my understanding should not be a very big issue?) However it still provides a risk. He is underweight and under muscled as well, and there is a possibility he has an ulcer. To top it off, the owner and current trainer have not been honest or upfront with us, not disclosing the surgery at all, and not providing any info regarding the horses weight condition. This being said, the temperment of the horse is wonderful: he's willing, level-headed, a quick learner, responsive, and all around a good seeming fellow. His gaits and jumping technique & ability are wonderful, and even my daughter (whom has back and arm issues and finds many horses very uncomfortable.) says he is very comfortable to ride. The owner has him priced at $20,000...In my opinion this is a lot of money for a horse with several ( unsolved) issues e.g. weight, lack of training, bad starting, and for a horse whom has undergone surgery. I was hoping somebody could provide insight ( or just an educated opinion) on whether I should go ahead and make an offer, and if so, at what price you might recommend?

Thank you,
TheHorseGeek