Sorry if this a dumb question but I plan to buy a good high end phone and than I'll buy a cheap decent phone so I can turn it into a hotspot for my more premium phone.
I'm not sure I understand the point. If you're going to buy a phone (especially a high-end one), why not just have your service on that phone rather than have to carry 2 devices?
You can buy a stand alone mobile hotspot unit and use it with a phone for Internet only, without service on the phone. You would obviously need service on the hotspot.