Initial Value of Real Estate

I have looked at a couple of companies that include real estate. Wondering if anyone has a good resource for a high-level valuation to see if the Buyer's asking price is in the ballpark of market value. I'm having trouble finding comparable information for recent commercial property transactions (warehouse, mfg, etc.). Don't want to incur the cost of an appraiser prior to signing an LOI but know this will be required as part of a loan. Thanks!