They need a way to track how much money is put into each car.
I have 2 tables, one for cars and one for repairs.
They are linked in a one to many relationship. One car can have many repairs.
My initial thought is to have a table for car attributes, and a table for 'Expenses' It may seem like symantics, but there may be more than just Repair costs associated with a car. You could have 'Repairs', 'Fuel', 'Taxes', 'Storage' expenses. If you had all expenses in a table you could have expense categories and sub categories. This would give structure for considerably more detailed data and business analisys. You would likely want one or more tables for list values to cantain types of Expenses, car models, etc.