I use the cash angle quite successfully to get a better price. Let's say there's a $400 item for sale that I'd like to have. I take $350 in my wallet, nothing else. I wait a few days on the ad to let it 'cure' for a while. Then I call, get an address and look it over. If its exceptional I beg for a price reconsideration. If its average, I take out the $300 of my offer and show it to them. That's my offer. 9 times out of ten, they see, smell and have already spent that $300.
So you can use the cash angle to your advantage with a motivated seller.
No checks, cheques, or Civil War or Confederate money. Chechs welcome any time.