Some hard thoughts on reality pertaining to your plans. All-wheel drive or four-wheel drive buses are hard to find, and when they do pop up, I suspect they will be relatively expensive compared to their rear-drive brethren. Also, with the weight of a larger bus, four or all-wheel-drive isn't always going to keep you out of trouble or get you out of trouble.
Also, consider that it is challenging to find parking for larger buses, and further consider that maintenance and repair costs can be much higher than you would see with a conventional vehicle. I only mention this because I know that most college students are broke, especially when they are fresh out of high school. I am in no way trying to shoot you down, but many newcomers experience issues they hadn't thought of, either through insufficient research, or simply being fed inaccurate info.
Ask anyone here with a complete and reasonably well done build how much it cost them, and if they aren't too embarrassed to tell you, you'll still be shocked at the amount. You can easily buy a stick and staple RV (sometimes twice over) for what many of us spend building a skoolie, but the trade-off is that we get what we want, built the way we want, and it is much more crashworthy and stormproof. Also, most truck repair shops are much more accommodating of skoolies for a multitude of reasons, as long as the build doesn't hinder serviceability.
If you plan on this thing being your long-term dwelling, there are four immediate considerations to be made. First, if in a southern state such as Georgia, air conditioning is a must. These things quickly turn into an oven in the summertime. You'll need a lot of insulation and a bare minimum of 13,000 BTUs of air conditioning.
Secondly, there is a lot of prep and demo work necessary in order to make these things a viable long-term shelter. This includes (not limited to) removing rivets and interior metal panels, replacing and upgrading insulation, ripping up rubber and sometimes plywood from the floor, removing and patching any rust, then building from there. If you can afford a bus with no rust, by all means, do what you have to do to get it, because a rusty bus will cost you enough time repairing it that it will veritably ruin your enjoyment of the project.
Thirdly, unless you have a definite location with reasonable utilities that can be counted on, you will definitely need to be boondock capable, which means a large battery bank and a large solar array, and / or generator capable of handling your electrical needs. Air conditioning and refrigeration are the single biggest loads on an electrical system. You will need this anyway if you are planning on going into the mountains for a weekend or two here and there.
Last, but certainly not least, skoolie owners can find themselves clashing swords with busybody NIMBY (not-in-my-back-yard) minded folks who are concerned about eyesore RVs and skoolies ruining their view or property values. Just because your buddy or uncle doesn't mind you parking in their backyard or driveway doesn't mean their neighbors won't stir up trouble and even fines from the local authori-tahs. And there will be certain roads and streets that are not legal to drive on (usually because the street cannot safely accommodate the weight of a skoolie, or a skoolie is wider, taller, or longer than the street is safely passable with.
There are also certain configurations that are to be avoided in selecting a bus. I learned the hard way to avoid larger Ford chassis models with hydraulic brakes.
So choose wisely, plan realistically, and build well. As I said, I am not at all trying to shoot you down, but I would hate to see someone just starting out in life get in over their head or in a bad situation because they didn't account for something in their planning.