party star keg v. party pig v. corny setup

Hey guys, I'm still relatively new to brewing (on my 4th brew now), and i'm starting to consider a keg setup. I know that it will be easier to keg my brews than bottling, which is why I want to go this route.

I've given myself three options, two mini keg options, and then obviously a full corny option.

I like the idea of the party options because I am still a college student, living in on campus housing (on campus apartment with a full kitchen, of course). While homebrewing isn't against the rules, kegging can be tough because of the "open container" policy the school's got. I can have a couple small kegs that are easily hidden, if anything ever happens. I'm worried about getting involved with the party systems though, because many of them aren't that much less expensive than the full 5gal system, and seem to last a fraction of the amount of time, and are almost more of a pain in the ass than they're worth.

I've done my research into the 5gal systems, and have even found a couple, decently priced kegs locally. I know that they are relatively small, and should be pretty easy to stuff into a fridge (I've got a mini fridge that SHOULD have enough room, but i'm not totally certain because it's not right in front of me at the moment, and won't be for a little while longer). My biggest question however is, how big does a CO2 tank really need to be? I'm a pretty avid paintballer, and have a couple old 20oz tanks left over from my early days in the sport. Can those be used? do they have a decent lifespan?

basically what it comes down to here is, are the party systems worth it in the long run? or should I just go all out and start with a 5gal system?

thanks in advance for the replies!

Get a corny setup and your your old paintball tanks. Even a small tank will run a handful of kegs worth of beer. Just make sure it can all fit inside the fridge before you buy everything, and use a party tap to dispense the beer. You could be kegging for like 50 bucks.

i'll be reunited with my fridge on friday and the first thing i'm gonna do is measure it for the required 23"
realistically i'll only need to have enough CO2 to do one or two kegs every month or two, and I may even be able to borrow a couple extra 20oz'rs from the local field.

can I use a paintball regulator? or should I buy a two gauge/stage beer reg?

It takes very little co2 to power a corny. You could even use the cartridge things. As far as the regulator I'm not sure it matters as long as you can set the psi to the correct range. Dual is cool if you want to serve two diff styles but not necessary

two different styles? (I don't fully understand why you'd have two).
I also plan on using the CO2 to carb the corny as well...I've read that you can carb and then serve one or two cornys with a single 20oz, is that true?

edit: now that I'm thinking about it, I think I have a couple old spare regs that I don't use anymore that I could use for this, since there's no liquid CO2 that will enter the reg, since the bottle is always upright. I just gotta figure out how to connect it all up

carb naturally with sugar instead of force carbing to save on gas even more

Doesn't that make for much more trub?