Before you decide on what size bus you want you need to decide how much bus you will need. The suggestions to put on paper some possible floor plans is a great idea.
Right now you will probably see RV shows being advertised. Go and see what they have to offer. There are only so many ways in which you can arrange stuff in a tube that is basically 8' wide (give or take a foot) and 20'/30'/40' long. Even look inside trailers and not just motorhomes. The floor plans in a trailer are not all that different from a motorhome.
Once you have determined your MoSCoW list you will be in a better position to determine which bus will fit your needs the best.
If you determine you must have a bus that can do highway speeds and climb mountains faster than walking speed you will need to be looking at a bus with a big HP engine and a heavy duty transmission with highway speed gearing. It is much less expensive to pay more for a bus with the power package that best fits your needs than to try and repower or regear your bus later on down the road. Remember the vast majority of school buses are spe'c'ed to transport kids to and from school at speeds less than 35 MPH. Outside of the trip from the factory there are some school buses that never go over 35 MPH during their whole service life. Those kinds of buses will not have big HP engines with highway speed gears. Those kinds of buses will usually have the smallest engine available and gearing to a top speed of 45-55 MPH.
When you get to the western states the minimum spe'c is usually for higher HP simply to deal with the bigger hills we have out here. The buses still may be geared to low top speeds. But they don't slow appreciably when they get to a hill.
Some western states, MT and WY in particular, will have dedicated trip buses with monster engines and highway gearing that will take advantage of the 80 MPH speed limits. Those trip buses will have the maximum head room, cross through under the floor luggage compartments, air ride suspensions, tinted glass, inside overhead parcel racks, and some even have killer sound and video systems.
CO requires all of their buses to have some sort of auxiliary braking system. Telma driveline retarder, transmission retarder, exhaust brakes, etc. will reduce the use of your service brakes to the point the service brakes almost never wear out.
Many CO, WA, and OR buses will come equipped with OnSpot automatic tire chains which makes traveling in the mountains in the winter a piece of cake.
So as you go shopping for buses you need to know what will work best for you. There is no one perfect bus. That is way there are four types of buses in many different sizes.
Good Luck and Happy Trails to you!
