Wow OK. I imagined 200k+
So a bus and a coach are a bit different but probably immaterial if you're going to refit and have it as a mega camper van. I wonder what licence you need to drive it? I would think you only need PSV if you were carrying passengers. One of those has probably got more space than my gaff!
Decades ago I worked for an electronics company and they needed a mobile lab/test rig that could do 70mph to simulate a helicopter at cruising speed. They couldn't afford an old National Express coach apparently, so they bought a shonky old Routemaster, tuned the engine to breaking point, and then realised it would not fit under bridges. So they cut the roof off, and put a hydraulic skirt under it so the roof could be raised and lowered. They replaced the seats with airplane seats, put 19" racking in for the TE, and a kitchenette.
Shortly after that, it blew up spectacularly, throwing a con rod and nearly castrated the driver. It was a legend, we used to get bus experts coming to see it.