No worries. I have a similar Barefoot Spa. It’s the Barefoot Spas MB7. Same thing pretty much just no lounge seat.
We paid a lot of money for ours a few years ago. Almost 15k if I remember right. Same M-Series as your ML7. I also noticed the prices went up on the website. See link: https://www.barefootspas.com/spa/ml7
4k seems like a good deal. I would jump on it. Just make sure it doesn’t have any leaks. You should ask to see it running with water in it before you do the deal.