There are a myriad of reasons to steer clear of older aircraft. They are cheap for a reason.
The GIV would be a much better choice.
Whatever you do, when purchasing older aircraft the better the pre purchase inspection the better off you will be.
Have a Google if corrosion and older aircraft. Let’s say during an inspection corrosion is found in the wing tip, cost...
Also doing the hours you are suggesting wouldn’t either charter or fractional ownership be better?
In addition the resale value of older aircraft is not good, your asset will depreciate fast.
I am sure there will be some brilliant advice to follow.
Good luck!