The iPhone appeals to people looking for a mobile Internet tool, a music player, a game device, and a productivity tool. But iPhones - when you combine the cost of the phone and the service contract - aren't cheap. Those who want an iPhone, but can’t necessarily afford the full bill seem to be left to two choices: buy another phone or go without. Neither’s very appealing.

But there’s a third choice: buy a refurbished iPhone.

Refurbished iPhones will save you some dough, but are the tradeoffs worth it? That decision’s ultimately up to you, but it you’re considering buying a used iPhone, here are the things to take into account and some suggestions for where to seek out your bargain.

What to Watch Out for with Refurbished iPhones

While a used iPhone can be a good deal, there are a few things you should watch out for to make sure you won’t feel a penny wise but a pound foolish.

Battery – iPhones are generally seen as having weak battery life. To compound that, their batteries can’t be replaced by the user when they die. A lightly used iPhone should have decent battery life in it, but anything more than a year old should be regarded cautiously. Ask the seller for as much detail about the battery life as possible or see if they’ll replace the battery with a new one before you buy. Also be sure to check on return policies in case the battery turns out not to be as lively as they claim.

Screen – If a refurbished iPhone has not been protected with a screen protector, its screen may be scratched.

That’s normal wear and tear, but scratches are less acceptable on the iPhone, since it's got a touchscreen for control and the media features that take great advantage of its 3.5-inch screen are one of its key selling points. Try to see the screen of the used iPhone you’re considering (even if it’s just a photo). If it's not possible, be sure to buy from a reputable, established seller who stands behind their products.

Capacity – While the allure of a lower price is strong, remember that used iPhones aren’t the latest models and that they’ve got less storage space as a result. Early iPhones offered only 4GB of storage, while the latest models offer as much as 32GB. That's a big difference and one that, if you've got a big iTunes library, can really affect your enjoyment of the phone. Be sure to weigh the savings against getting more for your dollar, and buy accordingly.

Features - Be sure you know what features you're sacrificing when you buy an refurbished iPhone. Early models lacked many of things the latest models have: 3G speed, the upgraded camera, the ability to record and edit video, true GPS, Nike + support, Voice Memos, and VoiceControl. Be sure that if you're buying an older model, you're OK not having the latest and greatest features.

Price – This holds true for price as well. A refurbished iPhone may be $50 cheaper, but is $50 worth getting something that’s not quite what you want? For some, the answer will be yes. Others will value the latest hardware and are willing to pay for it.

Contract Costs - Unlike the iPod, the iPhone requires a two-year contract with AT&T for phone and Internet service (in the U.S. at least). The rates for the original iPhone were a few dollars cheaper than for the 3G or 3GS. This isn't a huge savings, but may add up over time if AT&T continues to offer the lower-cost plan.

Warranty – If you can get a refurbished iPhone with a warranty – even an extended warranties - do it. The most reputable sellers of refurbished iPhones will stand behind their work. And a phone that's had one previous repair won't necessarily be trouble in the future, it might, so consider spending the extra money for an extended warranty (I think it’s the thing to do with new models, too).

Where to Buy a Refurbished iPhone

If a used iPhone is right for you, next you’ll need to decide where to pick up your new toy. But choose wisely.

From AT&T – Check your local AT&T store or AT&T’s website. The iPhone’s exclusive U.S. carrier sometimes offers refurbished models.

From exchange companies – Companies like NextWorth, FlipSwap, and Gazelle both buy and sell used iPhones. Their prices are appealing. See a full list of companies offering these services.

From iPhone resellers – Some companies that sell new iPhones also sell used ones. These mail-order or online stores usually offer prices similar to Apple’s.

From eBay/Craigslist –eBay and Craigslist are hotbeds of online bargains, but buyer beware. You may get stuck with a broken iPhone or a phone that doesn’t have the specs you thought you were getting, thanks to a scammer. Try to stick with reputable or known sellers, if possible.

Selling Your Used iPhone

If you’re buying a refurbished iPhone, you may have an older model you want to get rid of. If so, review your options for getting the most value out of your used iPhone.

When it comes to buying a refurbished iPhone, you can save money and get a good music player at the same time. You just have to be smart and careful about how and where you buy. With the tips above, you should be well on your way to doing that. Happy shopping!