First, we ALWAYS brought the item to the customer's home and set it up for him/her. We MADE SURE it was working properly when we left, and yes, of course we took a check or credit card (things were slightly different in the "old days" of the 1970's-80's)
Naturally, we both examined the item(s) and agreed on their condition and we had form that they signed agreeing. This was before smartphones, so pictures, other than poor-resolution Polaroids were difficult.
In all my years of business with the highest-end gear, I NEVER had a problem with this policy. If I did not know the customer, by delivering the gear to their home, I got a good idea of what was going on. The credit card was insurance, so I never worried. I would say about 3/4 of the time they kept the hardware and close to 1/2 the time they kept the speakers.
Going out and setting up whatever it was helped me make the sale. If your dealer does not do this, I would find another dealer if you can.
Cheers!