I'm also going to say a fixed gear PA-32. A Cherokee six or fixed gear Saratoga. The mission calls for a six seat airplane with a healthy useful load but OP also needs something that isn't hard to handle and won't look too scary to an insurance company. I wouldn't want to see what the insurance premiums for a retract with a student pilot are right now... if you can get insured.
A fixed gear PA-32 won't be much harder to fly than a typical trainer Cherokee. In your area with the high terrain a turbo might be nice but it might be hard to find a fixed gear turbo PA-32. They exist, at least with aftermarket conversions but they're not common. A turbo is good for taking off at higher elevation airports and climbing high, however you'd probably be fine in a non-turbo just be mindful of density altitude.
OP also mentioned pressurization, most piston aircraft of the type you'll be looking at aren't pressurized. Typically if someone wants to go high they get an oxygen system instead.
There are nicer planes out there in OP's budget... Turbo retractable gear PA-32s, A36 Bonanzas just to name a couple. If you really want to go that route, try calling insurance companies to see if they'd cover you and about what you'd be looking at for premiums. Sometimes it's better than we'd think, you never know. Still, a really nice fixed gear Cherokee six could be had in the $100-150k range and it would be a great starter plane. That would be my vote.
