Answering the topic titles question, IMO spend what you can afford.
Van buying is a lottery!
You can have loads of problems with a low mileage example and not one problem with something that has gone to the moon and back and vice versa.
My first van, that is now our training/gutter cleaning/ pressure washing van has covered over 200,000 miles, I have had a ball joint fitted, new starter motor and an odd tyre. On the other hand I had to scrap a lovely clean low mileage full service history berlingo after 6 months.
Go for a newer transit connect and swop your gear from your old one.