I wrote this awhile back on this site. Maybe it will be helpful.
Don't be fooled by horse power ratings. What you want to look for is CHP not HP rating. That's continuous horse power rating. You might see a treadmill that rates itself at 2.0 hp when it only has a CHP rating of 1.0 hp.
You need at least 2.0 for a running treadmill. 2.75 CHP is what I recommend. Good treadmills cost a lot. Cheap treadmills break and feel like junk to run on. Maybe walking is okay but you can instantly tell the difference when running.
You might be able to find a usable cheap treadmill for around $700-$800 but I doubt it. One of the original running treadmills is Pacemaster. They have a model that sells in stores for about $1700. Another good brand is True. I own the cheapest one and it cost about $1800. Lastly if you can afford it is Landice. They are expensive. All brands can have problems even the best mentioned. You can put the odds in your favor though by buying quality.
Don't be confused by treadmills talking about how fast they can go. In general they all have the same speed claims. My treadmill goes up to a 6 minute mile. The incline goes up to 12 degrees.
Also don't think you need a display board that looks like the control panel for a space ship. Keep it simple. You need a speed button and an incline. My True model shows you running around a simulated quarter mile track that is the standard distance for Track. You need to change between miles per hour and how many minutes it takes to run a mile. No one in track says they are going for a 10 MPH run pace. You will hear let's keep it at a 8 minute mile pace. MPH is meaningless for serious runner. It's a nice feature to have both on a machine.
Most guys using a treadmill on this site don't give a damm about running but just want to get ripped by doing cardio. If you see yourself just fast walking on a incline a cheap one might work. If you like to run regular spent the money. Walking fast on a treadmill on an incline is tough work.
So the short answer is Pacemaster, True and Landice for a quality home treadmill. Their cheapest models cost a good buck but they are quality items.