IMHO broken down on the side of the road eventually happens to everybody, so have at least $500 saved up for vehicle emergencies. No matter whether it's a bus or a car.
As you jump in (or before?) get a vision of what you're building and where your personal life is going -- for example, if marriage and family are in your plans for the next 10 years, consider whether you want to build a bus that can be fun now and adapted to suit that lifestyle when it comes, or whether you want to build it for your lifestyle as it is now/in the near term with the understanding you'll be parting ways with it if/when family happens down the road.
Also consider whether you'll be going away from home for college, and if so, whether you'll be able to store it at home or may have to pay for storage to keep it closer to you at school. Or whether it might be your full-time residence while at school -- keeping in mind that in most climates, this means a much more thorough (expensive) conversion job. You'd still need a place to park, though, and that usually won't come free.
Go for it!