Go ahead and do the inspection, but do not release the written report until after you have been paid AND the contract is signed.
Once they have your report in their hands, you have nothing left to bargain with. If they are on a tight deadline or out of town you have more authority and control over the process.

If you do not take Visa/ MC you should start.

You have a business to operate, operate it like a business.

Schedule the appointment.
Get payment up front.
Inform them you will send them some papers to FILL OUT.
Do the inspection
If they ask for the report, say. I haven't received the agreement back from you. Can you send it now?
When you receive the agreement back, send the report.

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Rick Cantrell
Columbus GA