Interesting to hear that I would have to be prepared to pay the trainer a percentage of the sale price. I also want to ask, how much does a presale vet check cost and would another vet check be necessary if you were getting ready to purchase? I'm sure it'll be fine with my mom if it's upwards of a few hundred dollars. Vet checks vary by vet, services rendered and your locale. I expect to pay between $200 & could be as much as $1000 if I have a lot of radiographs and bloodwork done. But that would only be done on a very expensive horse, for instance one that's already a National Champion at something.
Paying your trainer either a percentage (probably 5-10% of the price if they aren't representing the horse) or a flat fee, I'm used to between $100 - $500, depending on just how good the trainer is; is fairly common. You are taking up time they could be spending making money with lessons or working a horse in training or taking up their day off to look at a horse you may or may not buy.
Also, one of the horses I'm looking at is a little over at the knee, and I'm curious, why is being over at the knee or under at the knee looked at closely? Does it just "damage" the horse's conformation? Or is there something more to it? A 'little' over at the knee is not a big deal and some folks prefer a hunter to be a little over. It just means there's not a straight line from the knee down. Anything exagerated wouldn't be good but a little over isn't a huge deal. Many horses run for years and jump for years with no lameness issues because of it.
I am looking at horses for basic english of course, and jumpers in particular. So I do feel like having a trainer would make a difference I just don't want to have to end up paying a lot just because she came and gave me her opinion and what not. But then again, it could be worth it. Having a trainer with you, to look the horse over, test ride it and evaluate it and give you her professional opinion can literally save you thousands of dollars or even your life if it's totally the wrong horse for you or misrepresented.