eagles_dare13

I value privately held companies like this all the time at work, mostly related to estate tax filings, eminent domain, shareholder disputes, and sometimes even transactions.
For a car dealership with under $10M in annual revenue, I would try and get transaction data for other dealerships around that size. Pratt’s Stats and BizComps databases could be good resources, and they may have free trials available - I don’t know. Public company multiples may not be applicable in that scenario - they are just too big.
I wouldn’t bring up the discounts for lack of control or marketability either, especially for the purpose of a negotiation.
Lastly - don’t forget the asset approach. Although the company may be “doing well”, often times the indication of value from the earnings is below the value of the assets. This happens a lot with asset or working capital intensive businesses (e.g., a ton of machines or inventory).
Good luck!