I just found a Lifehacker piece on buying used stuff without getting ripped off. I have plenty of experience in this area.
The key, I think, is to deal in person, and test as much functionality as you can before handing over the cash.
For example, a decade ago I bought a Playstation. The previous owner said he was pretty sure it worked, but he didn’t have any games anymore. I asked him if we could hook it up and play an audio CD in it. He agreed; the disc played fine, and based on that I was willing to buy the unit. An audio CD tested enough of the unit to give me confidence that it all worked OK. Indeed, when I got it home and put a Playstation disc in it, it played fine.
When I buy a used computer monitor, I routinely power it up. If it displays something on the screen saying it’s not getting a signal, I’ll buy it. If I can’t turn it on, I’m willing to take a chance if the price is low enough. Back when a working used 15-inch LCD monitor was worth $50, I bought a couple for $5 on separate occasions, untested. They worked, as it turned out. At $5, the price was low enough that I was willing to take a chance; the cables are almost worth that much. More recently, I’ve picked up a 19-inch unit for $12 and a 20-inch unit for $30.
The failure rate for LCD monitors is much lower than it was for CRTs. I bought my first LCD in 2006. I’ve only lost one in eight years. I thought it was remarkable when I got four or five years out of a CRT.
I also buy a lot of used appliances. My wife and I own and manage rental properties, and as long as the existing appliances work, we leave them in place. When the appliances are missing, buying dependable used appliances keeps our costs under control. If you can test the appliance, that helps, but it isn’t always an option. A quick visual inspection helps. You’ll know neglect when you see it.
Knowing your brands also helps. Based on Consumer Reports ratings, I prefer appliances made by Whirlpool and GE (especially washers and dryers made by Whirlpool and ranges made by GE) but when I don’t have any other choice I’ve done fine with Electrolux-made (Frigidaire) appliances as well. I don’t mind off-brands made by those companies–this chart helps you determine that. Basic, no-frills models sell cheaply, and they’re the most commonly available since people will sell those to replace them with higher-end models with more features. But the basic models have fewer things that can break and the parts are cheaper. In fact, one reason I prefer Whirlpool-made washers and dryers are because replacement parts for them are cheaper than for other brands.
Also keep in mind that appliances repair is possible, and when you pay $100 for each appliance rather than $350, you can afford a repair or two and still come out way ahead. You can also do many simple repairs yourself, rather than paying for a service call.
I also don’t worry about older washers and dryers that look dated. While the white bodies and dark tops may evoke memories of the 1980s, those older appliances were built to run forever.
But I absolutely won’t buy a lawnmower unless I can try it out first and make sure it starts. That said, if it starts, I’ll buy it. Any lawnmower will turn to junk very quickly if you neglect it. But if you start out with a mower than runs and you’re careful to keep fresh gas in it (no more than a month old, ever), put a capful of Marvel Mystery Oil in each new tank, put synthetic oil in it instead of the overpriced nondetergent motor oil from the hardware store, and change the air filter and spark plug at the beginning of each mowing season, just about any mower can give you several years of service.
Frequently people ask me how I dispose of the old gas. I pour it out into a clean plastic pan, pour the pan into my gas can using a clean funnel, then pour the can into my car. If my car has 10 gallons of fresh gas in it, the additives will mix with the gallon or so of junk gas. Then I buy a gallon or two of fresh gas to fuel up the mower.
If a lawnmower looks pretty new but doesn’t start, there’s a good chance the previous owner wasn’t doing those things and the carburetor is full of crud. It’s not hard to find people who fix lawnmowers for extra money. I found a guy a mile or two from me on Craigslist, and people like that frequently advertise on the bulletin boards at your local grocery store. They’ll generally fix it for around $50. If you can buy the mower for less than $50, that’s cheaper than buying a new one.