First, let's define "SDE" or Seller's Discretionary Earnings. SDE is defined as net income before deducting the primary owner's compensation and benefits, other discretionary, non-operating, or non-recurring income or expense, depreciation, interest, and taxes.

Business Value can be determined by the following:

Gas Station with a convenience store, 2 or 3 times the SDE, plus inventory. With Car Wash 2.5 to 3 time SDE, with garage/repair 1.5 to 2 times SDE. (Prove the numbers through gas receipts and store invoices)
Minimum inside store volumes. Figure $30.00 per 100 gallons sold per month. Example if a station does 60,000 gallons/mo the inside sales should be a minimum of $18,000/mo.

Note If a gas station does 150,000 gallons per month and has a gas margin of 10 cents per gallon and convenience store sales of 45K per month. (with profit margin on C store sales 25- 30%), this is an example of a good opportunity. 

"Rules of Thumb" for Purchasing Gas Stations