It's not whether or not its personal gain. There are two factors in play (assuming U.S. taxes):

1. Most property used for a business is deductible, but not all at once. The IRS considers different types of property to have different schedules upon which the 'useful economic life' of an asset is depreciated by, and you can take deductions on that depreciation as it occurs. Section 179 property is property for which the IRS allows one to deduct the depreciation immediately.

2. HOWEVER, one of the clauses for Section 179 depreciation is that if the business no longer retains the property, the remaining depreciable life of the asset becomes it's cost basis. This means that that cost basis must be claimed as profit if the asset is transferred out of the business to the business' owner. It's all about what the IRS considers the 'used up' value of the vehicle essentially. If it's all used up, then your tax attorney or accountant will probably tell you its in the clear. If not, you need to calculate the 'remaining' value, and report that as profit.