Honestly? You are looking to buy or lease a “tired” 17 year old Friesian to ride a slow Hunter Pace, to do low level dressage, and to hack out?
Just don’t do it. There are many horses that can do what you propose and they will come younger and better suited to do what you want to do with them.
Why the Friesian? Black? Long mane and feathered fetlocks? There is an old saying; “pretty is as pretty does” and you will be much happier if you take the time to find a horse that is suitable for the purpose in which you intend to ride it.
This one sounds not-suitable-whatsoever, for what you are looking for in a horse.
I can’t imagine any honest person trying to sell you this horse when/if you have told them what you are wanting to do with it.