My bus is a party bus by my standards. However, by the standards of the state of Minnesota, it's just a harmless RV. What you need to do is sit down and really lay out what you want to be doing with this thing. How many people are you going to want in it? Is it going to be moving with all those people in it? Is there going to be alcohol or even intoxicated individuals involved while moving? Are people going to sleep in it? What kind of electrical and plumbing systems are you going to want? The list goes on and on. Sit down and figure that out for yourself and then maybe post it on here and we can give you some feedback.
I'll start by being "that guy" and pointing out some obvious limitations. Maybe it will be easier to take from someone who's only 6 years older than you.
1. You can have no more than 15 people including yourself in the bus while it's driving without a CDL. I'm not aware of any state that allows even in intrastate CDL to anyone under the age of 18.
2. You can not get paid by anyone (under the table compensation for gas would probably be ok) or you put yourself back into the CDL thing again.
3. Going to clubs or any other populated area will always raise the question of whether or not you need a CDL. Even if you are legal, it might take a long time to convince a cop of that. This is especially in downtown Minneapolis.
4. You are a minor. That makes consumption of alcohol a risky thing. I'm not your parent so I'm not going to say one way or another whether or not you should drink. You wouldn't listen to me anyway, right? I will throw this out there though. If your bus is registered as an RV and PARKED, the police cannot search it without a warrant assuming they can't see any wrongdoing. These are the same rules that apply to your house. Keep it quiet and out of sight and you're homefree. However, get out on the highway and get pulled over...well now you as the driver are in possession of any alcohol on board which is a problem since you're underage. Also, any passengers on board maybe subject to underage consumption unless you get a cop that likes the idea of being a really big sober cab. The laws for search and seizure are also different for vehicles versus houses. It will be a lot harder to keep police from searching and finding anything else you or your passengers may have brought aboard.
5. Buses cost money....lots of it. Party people WILL break stuff. Basic parts WILL cost lots. Don't think that the cost of the bus is just what's on the sticker, even if you keep it simple.
6. Young women like buses. Young women LOVE dancing on buses. Any foolish actions such as that can make you dangerously liable. Just be careful.
My advice? Go for it! You'll have a ton of fun and when you grow out of your party bus phase, you'll already be armed with knowledge for your next conversion.
I'm not sure how to convince your parents that it's a good idea. I will say this much, however....DON'T INTRODUCE IT AS A PARTY BUS! Call it a camper or something else. Don't use that p-word! Having some well drawn out floorplans, timetables, budgets, costs of ownership, etc all ready might also help your case.