Yes, sellers will often haul a horse to the vet of your choice
for a PPE done if it is a upfront known part of the plan. Do not use a vet affiliated with their vet or practice.
The seller is not paying that PPE bill so is not owed any information either unless you choose to share it.
They seller may ask for some money as it is their time and rig being used but it is their horse being sold contingent on a outcome acceptable to you.
Some owners may indeed tell you you can take the horse, but more common in my experience is owner hauled to purchasers vet location for exam to be done.
The costs though are all yours to incur...ship, exam..but information is also yours not theirs.
Costs for the exam can vary greatly dependent upon what is needed done...
Are you looking for a general wellness check-up or are you wanting all the bells and whistles checked with full x-rays, flexxions, diagnostics and or ultrasounds, bloods drawn and sent out..
There are many variables in pricing for this reason and at any point you not like or the vet advises you of a issue you will not tolerate...then the vetting stops and you pay only for what has been done.
Depending upon your agreement made, the sale of the animal may take place right then and their and if acceptable findings you pay for and the horse is delivered immediately...
All those details need worked out in advance once you find the horse of your dreams.