Since goodwill is the sales and profit-making capability of a carwash business now and in the future, the value of personal property assets is only incidental to the future of the carwash business. It follows then, that price of the cash business should be evaluated by capitalizing future earnings. As such, there would be a number of things involved with the price assessment including but not limited to:
The desired return on investment
Conditions and terms of the lease
Assessment of facility, market potential, competition and management
Income and expense verification and reasonableness
Risk adjusted calculation of value
You may want consider taking some of the risk out of the deal evaluation by enlisting the services of a qualified industry consultant or appraiser that specialize in providing opinion of value for carwash.