I'm going to assume by loan, you mean you loaned the sum necessary to buy the business.
If that is the case, then
calculate and post partial year depreciation on the vehicle
then create a loan asset account, due from [name] or something
journal entry
debit vehicle fixed asset account for the total in that account, credit due from account
debit due from account, credit vehicle accum depreciation account for the balance in that account
debit due from, and credit all other assets that were part of the sale
( if inventory items were involved do not use a journal entry, instead use inventory adjust, set the adjusting account to the due from account and set the qty of all inventory sold to zero)
the deposit you received, set the source (from) account to the due from account