First of all I would suggest you get a better accountant.
When you buy a bus and put it into business service, that is when depreciation starts. You can depreciate it under several schedules not just the first year big deduction mentioned above. if it has a service life of 3 or 5 or 7 years you can choose that time and do a straight line depreciation. Depends on how long you plan to use it for business and in what years you want the expense to offset income.
I pro rate my bus used between business and personal travel, a varying percentage each year. I add up all the expenses of owning it ( fuel, maintenance, insurance, etc...) and the business percentage of that is a deduction to my business income.
Be wary of the mention of "credits" in prior posts, there is a big difference between a tax deduction and a tax credit.
Seriously, I think your accountant needs more education, and I do not think it is your job to do that, find one who knows his stuff better.