A while back, I decided I needed a home gym. I work from home, I've never been good at motivating myself to travel to a gym, and my exercise regimen, which at the time consisted of a few hours of biking a week, needed a kick in the pants.

The basement room I use as a home office has plenty of space for exercise equipment, but I didn't want it to get too crowded, so I focused on equipment that could be folded up. I got a good treadmill for running indoors and a complete Bowflex home gym for weight work, which I chose partly because of its relatively light weight and partly because I've been reading positive reviews about it for years. And I added a NordicTrack, because I like having another choice for cardio work.

My total cost for all of that gear? $150.

Wait, did you rob an informercial or something?
No. I subscribed to my local Freecycle list, surfed Craigslist, and kept my eyes open. The Bowflex -- a few years old but literally like new -- was free from someone who was getting married and needed to clear out the house. The NordicTrack, also practically new, was $25 from a local who advertised it on Craigslist. The treadmill, another Freecycle find, was free but needed a $125 repair, and now it's like new, too. If I had bought all that stuff actually new instead of like-new, it would have cost me more than $3,000.

I've talked in the past about the advantages of buying nearly new used cars, but there's a whole huge marketplace out there that's full of great stuff besides cars -- much of it cheap or free. Lots of people buy things with the best of intentions only to leave them gathering dust, and when it comes time to clear out the clutter, they often let things go for very little.

Exercise equipment is a classic example, but there are lots of others, like musical instruments, tools, cameras, all kinds of sporting goods -- the list goes on. Add to that the folks who just have to have the latest new stereo system or carbon-fiber road bike and are willing to sell last year's latest new thing for a huge discount, and you have quite a supply of great stuff available cheap, if you're willing to live with a few scratches here and there.

And finding all that stuff is easier than ever these days.

It's that Internet thing
The Internet has changed an awful lot of things over the last dozen years or so, but its ability to match buyers with sellers on a global scale has driven some of the most profound changes -- particularly when it comes to used stuff. Companies like Amazon (NASDAQ:AMZN), with its extensive used book department, saw the possibilities early. And of course, the founders of eBay (NASDAQ:EBAY) built a wildly successful business around what is essentially a giant virtual flea market.

More recently, the Freecycle movement has led to the creation of thousands of email lists for people looking to unload or acquire usable stuff for free. And Craigslist has all but replaced the old newspaper classified ads across much of the world, with marketplaces for nearly anything you can think of.

Live large, save money
The existence of these marketplaces probably isn't news to you. But next time you're thinking about making a major purchase, especially of something that's recreation- or hobby-focused, check these marketplaces out. They're not just for people on tight budgets -- I know plenty of successful professionals who regularly get lightly used camera lenses or sporting goods or guitars via eBay or Craigslist for a fraction of what they would cost to buy new. A careful used purchase can be a great way to save money -- or, alternatively, to get a higher-end piece of equipment than you'd otherwise be able to afford.

And you know what? Nobody will ever know.

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Fool contributor John Rosevear will probably never be as buff as the guy in the Bowflex infomercials, but he's having fun trying. He does not own shares in any of the companies mentioned. Amazon and eBay are Motley Fool Stock Advisor recommendations. The Fool's disclosure policy is rock-hard muscle.