When I purchased a treadmill many years ago, I started by looking on sites like sports authority and Sears. I narrowed them down by the features that I wanted, then I looked at reviews, and then price. It actually was pretty easy when I followed that procedure.
Check out the brands offered at costco. They only stock good ones. Consider the weight of s treadmill and how you will transport it. We bought new at costco, as their price includes delivery and a flight of stairs. (It’s in the basement, so this was important). Most stores will tack on another $100 for delivery and another $100 for stairs if they would, as some of the deliveries are to the curb.
No Costco in our state I’m afraid. Though I heard a rumour one will open in the nearest city to us in fall 2015.
I agree with those that say I need to try them out before o buy one. Nearest place I can do that is about 100 miles away and that is not possible right now.
During my self-conscious bad knee years, we had an elliptical trainer. I don’t remember the brand, but I do remember that it was pretty expensive before we got to one that was comfortable to use and had a long enough stride. One advantage to an elliptical that was very important is that you can’t limp–you must have the same stride length on both legs. Since I had a bad knee, that was important–at that time, even walking (much less running), my stride was asymmetric.
If you have any friends who use a treadmill or have their own elliptical machine, ask if you can try theirs. If you have local health clubs, talk to them about trying the machines they have (then you’ll know what to look for used).
Ultimately, I found the exercise machines in the basement–which my husband used regularly–so unpleasant to use that I considered them an incentive to be outside in all weathers and conditions. However, I know lots of people who find TV and other distractions lead them to workout longer and harder. Me, I just take the dogs and go.
Landis or True (sp) tm. We are looking at a Landis to replace a Life Fitness tm we had for ten years that I wore out. I never really liked the Life Fitness one: it bothered my hips and the console was enormous. It was a surprise birthday gift, though, so what could I say?
If you can try them out, do. See how big and how loud they are and how they feel when you walk/run on them. Make sure you can see over the console to the TV! I could, but my kids couldn’t until they got taller.
I love the idea of a second hand one. There must be plenty of gently used ones.
What I meant by checking out costco, it that they genrally do a good job at selecting products that have good reliability, so you will get a better than average product.
I have found I like a wide and long deck, as I have a very long stride. A folding deck is also a good idea to save some space.
Here’s their current online offering:
http://www.costco.com/treadmills.html
One recommendation for your treadmill is to plug it into a surge protector. We had one get fried in an electrical storm. We now keep it and the elliptical unplugged when they aren’t in use.
We are looking at ellipticals. I want a treadmill but DH wants an elliptical and he will use it more. Costco is having a sale on a decent one.
I’m in the try it out camp. If the treadmill doesn’t work with your stride length, its unpleasant to use. The one my folks had was like that and I never felt comfortable using it. I’d always trigger the stop because my stride was longer than the treadmill platform or something. If any of your friends or relatives nearby have equipment you can try out, that would certainly be ideal, or the Y or health club. Good luck!
One more installation tip: never put motorized exercise machines on carpet. The lint from the carpet will get sucked into the motor shortening its life. Use a special mat ($50 or so from Amazon) or plastic chair pad large enough to cover the space under the bet of your treadmill.
We bought a Precor treadmill because it was made at a factory located a few miles from my house. I also happened to like it. We never paid for fancy programs and bells and whistles, just got a commercial grade machine that has one user functions.
I have a Lifespan 1200i that I bought a couple of years ago through Amazon. It’s great: sturdy, a decent number of pre-programmed routines, good incline range, ability to download exercise info to one’s computer if desired, etc. I did quite a lot of research before I bought it to find something that was good and sturdy and functional but didn’t cost what the kind you’d find at a gym would. I wanted a treadmill that I could walk on at various speeds and levels of incline, not something to run on. I’m sure someone could run on mine, but I don’t.
I did use Treadmill Doctor, and probably other sources that I don’t recall.
I’m a Y member (and use it four or five times a week). Last year we got all new fitness equipment and I wondered if they had a lease agreement that included periodic replacement. Where does all that older gym equipment go? I think if I ever decide to invest in a treadmill that would be one of the first things I’d look into. The outgoing Precors all seemed to be working fine as far as I could tell but one day they just disappeared. 
Sometimes gyms will sell old equipment, and if it has been maintained in can be a bargain. With treadmills, if you are talking walking on it, most treadmills IME will do the job, there isn’t the wear and tear that you have with running. I have a Nordic track 900, that cost around 1,000, that works great for walking and also is okay for interval running/walking, but I wouldn’t use it for continued running. The more expensive treadmills tend to have better suspensions on them, and that believe me will save your knees, some treadmills your knees get hammered. Gym class units are in the 4-5k range and are big and heavy, but there are units in the 1500-2k range that are decent for home use, or you could get a pro unit used. I would look at some of the fitness magazine websites, they have gear ratings that talk about things like the impact of running on them. CR isn’t bad, they point out certain things, like how rugged it is, and also things like motor size which can be important as well,and their buyer guides, even if I don’t like their ratings, so say important things on what to look for.
If your knees are in issue, try a recumbant bike as an alternative, my wife has wonky knees and she uses the recumbant to do interval training, and it really works with her legs. Lot more compact then a treadmill, and a good one is a lot less expensive then a good treadmill:).
As a side note to my original post…the incline treadmill we have does take up some space and also, you need some ceiling clearance as well sine when inclined, it goes up quite a bit. But the workout is so much better than a regular treadmill and pain free on my knees , back and hips
We got a Precor Elliptical about 8 years ago from a gym. It was reconditioned after its “retirement” and has never given us any issues save for some needed routine maintenance. We found it through eBay. I think for ellipticals and/or treadmills, I (personally) would ONLY go with gym-quality equipment since I tend to be bothered by squeaks/rattles/vibrations that many people don’t notice.
Like the Princess & the Pea, I guess.
You are not alone. Running on a treadmill is boring. Running on a rattling, squeaky treadmill is pure torture! 
There are sites that sell refurbished gym equipment, but I have no experience with any of them. Maybe someone who has bought from such a site will chime in!