My only end-of-year asset is a van. It is worth $18,000. What is the number I put in the TOTAL END-OF-YEAR ASSETS portion of my Balance Sheet.

If your ONLY asset is a van worth $18,000 at the end of the year, then your total end of year assets would be $18,000. You would enter the beginning of the year amount and then the depreciation.  This would give you the end of year balance.