As a draft cross, I'd have him tested for PSSM1 during those first 30 days, if he passes the PPE and you really like him.
Percherons have some of the highest instances of PSSM1 and, while PSSM1 is manageable, it entails a LOT of work and might be overwhelming for a first time horse-buyer.
The undermuscling of this particular horse's hindquarters makes me really question his status. Many of the horses listed on that website are thinner than I'm used to, but this guy looks different. He looks very undermuscled, vs simply underweight.
Here's a link - Polysaccharide Storage Myopathy (PSSM)
Animal Genetics is the fastest lab for the test, you'll have results back in under 2 weeks. You can pull hairs for the test and send them in all by yourself - no need for a vet to do it.
Edit: plus, not to be a downer, but truly "perfect" horses don't get passed around like it sounds like this guy has been - in my opinion. That sounds bad, but genuinely perfect horses tend to find a home and stay there for some time - not get passed around and end up with a trader at age 10.
I'm sure there are some horses that are perfectly perfect that have been passed around numerous times in a few years, but it's not typical, imo.
My gelding has a similar story - "saved" from neglect at age 4 by a guy who trained him, then was ridden around for a year, then became a pasture pet until he was 9, when he was sent to an auction and ended up in the kill pen. A flipper bought him out of the kill pen, sold him 60 days later with a false story, and he stayed in his next home for about a year and half before becoming mine.
I figured he just had had a bad run, he needed to get lucky and find his person.
On one hand, I was right - our personalities meshed from the day we met and he is MY horse, through and through.
It's turned out that he also has a genetic disorder that renders him essentially unrideable, he's relatively unpredictable, and he's extremely high-maintenance. He needs to work every single day, or he's in extreme pain the next day.
That's just my take. These days, I raise my eyebrows at middle-aged, grade, horses with limited histories and anything less than stellar training. Maybe I'm right, maybe I'm wrong...but my gelding has turned me into a skeptic.