Although it's not foolproof, I do have a process that can help with that: it's called "turn the pickup run into a mini-vacation with the wife".
I once bought a pair of JBL L220's from a guy that lived up in the hills outside Ukiah (I'm in San Diego which is a good 10+ hrs south).
Wasn't really expecting to win the auction, but having just missed out on a similar buy on a pair of 4315's a few weeks before that, I said screw it and threw a bid down anyway and damned if it didn't hold up. Uh-oh, now how do I get them home and oh yeah, where's the cash coming from? Details...
I thought about how to pull the whole thing off for about a day, during which I signed up for a PayPal credit card that came with a large enough credit line that I could pay for the speakers at least, w/o having to sell something else first.
Then I waited for the wife to sit down that evening with her cocktail before walking up and saying "we should take a little vacation" to which she responded "what the hell have you bought now?", lol.
It worked out ok though, we rented an upscale SUV big enough to fit the L220's in the back and drove up to Napa/Sonoma/Healdsburg, spent a couple days in that area doing the usual wine and dining fun stuff. On the last day there, we drove up into the mountains (including a long dirt road at the end) and picked up the speakers, seller was very hospitable and that part went seamlessly. Drove the speakers back to San Diego spending another couple of days in the process in Monterey and Santa Barbara along the way so overall it was a success. I haven't tried that approach since, though!
John