I agree the info is kinda spotty. A link to the actual Craigslist ad might help with advice. Seeing as it is an 80s-90s Ford truck chassis over 1-ton, however...
The VERY first question you should ask is air brake or hydraulic. From my understanding, the Lucas-Girling hydraulic brake systems on these are apparently a nightmare and very hard to get parts for. AFAIK, these were unique to Fords over 1-ton, and believe these have been out of production for some time. My former B700 had this system, and I have seen a 96 F650 box truck with it. Not many school buses had air brakes in 1993, so it is likely the system I speak of. From what I gather, most shops won't touch them, and those that will, will likely charge a king's ransom for brake service. If it is indeed hydraulic brake...
If the parking brake actuator is a flip-style toggle switch mounted in a black box with a yellow label, that is a dead giveaway -- That switch is the actuator for the parking brake, which I understand is a hydraulic unit that acts like a spring brake on a typical air-brake system. Typical brake service on these beasts can run $2000 or more just for the rear axle, which is what happens when people with college degrees and no common sense try to re-invent the wheel.
An air-brake bus would have a simple yellow diamond-shaped air valve handle. Most of these were hydraulic, but if it's air-brake and all else checks out, it could be a very good buy. Air brakes do not necessarily require a CDL. CDL is only required for certain vehicles, usually over 26k lbs GVWR, and I can tell from looking this one isn't even close. My 64-passenger only had a 24,100 GVWR at nearly twice the length and 3x the passenger capacity.
If this one does have air brakes, at most, you MIGHT need an air-brake endorsement -- which MIGHT require an upgrade to a Class C CDL - MAYBE. I doubt it though, pretty sure RV's are exempt from CDL requirements - an exemption I don't care for, as a CDL driver myself, but DOES apply once the title has been changed from BUS to RV or MOTORHOME. I WOULD, however, strongly encourage educating yourself about operating a vehicle with air-brakes, should this be the case -- They're not complicated, and quite reliable, just a few things you should know to keep small problems from becoming big ones. In the interest of safety, if necessary, I'm willing to walk anyone through the basics of air brakes - email me. A commercial driver's manual (available at most DMV / BMV offices) will help with this, they have an entire section dedicated to operating vehicles with air brakes.
Not trying to poo-poo this one simply on the brake system, but the last thing you need is to be stuck somewhere with worn-out brake linings and/or hydraulic fluid pouring out, blowing your wad on repairs, or worse, unable to get help with it at all. Also consider that these use a second engine-driven pump on which a broken drive belt will keep the parking brake from engaging or disengaging until it is replaced.
I would pass on buses with the Lucas-Girling brake system, just my $0.02. They work fine until they don't, and when they don't, well, be prepared to spend half, if not the full amount you paid for the bus, or more, to fix the brakes. But don't take my word for it -- Google 'Ford Lucas-Girling hydraulic brake system' and see what you find. Contact truck repair shops and ask them what they charge for brake system service on 2+ ton Ford trucks / buses with the Lucas-Girling system, or whether they will even touch them.