Getting a treadmill is a great idea for the house, especially if you are limited on time. We have an elliptical at our house and it's been great to use it for when I have to pound 1-2 hours of cardio out to prepare for certain events (photo shoots or body building competitions). We plan on getting a treadmill in the near future as well. It's also been a huge convenience for my parents, especially since my Mom has high blood pressure.
As far as which brands to go with, that all depends on your budget, you get what you pay for and the more you put into it, the more you get out of it from a quality standpoint. One thing to note, if you do buy a full blown commercial treadmill, make sure to check the voltage requirements. Many commercial treads are either 120-220 volts that require a NEMA 5 plug, therefore you'd have to get an electrician to rig up the location of where you plan on putting the tread to handle that requirement.
If you are not limited by space, stay with a platform tread over the fold up, in general you tend to loose a little structural integrity on the fold ups by virtue of there being more moving parts in the frame.
There are 4 brands that worth looking into. If you are looking for the best bang for the buck at the mid range level, True Fitness (their PS line) is the way to go, heavy 11 gauge steel, 3 HP 'Continuous duty' motor, big running surface (22 x 60 I believe), basic programs, wireless and contact HR, 15% incline. You need to choose if you want the PS100 (standard belt) or go with the upgrade PS300 with the ortho belt for better cushioning. Their top of the line in the PS category is the PS 800. Check out their website for the differences. You are looking at spending the mid 2k to 3k range.
Life Fitness their 5 series, T-5 to T7 are their best line. They use a lot of commercial components on this tread ie. belt, gauge of steel, thrust motor etc. etc. Life Fitness is a name brand we see in most gyms and has a reputation of having one of the most comfortable running surfaces in the industry. You are looking at mid 3k to mid 4k range depending on which one you go with.
Precor is the other major line in the fitness industry that we see in the clubs. Their 3 series 9.31 to 9.35 is the way to go, the 2 series is okay, but stick with the 3. This is probably the quietest tread in the industry bar none, almost feels like you are running outside with how the software responds to belt speed and foot speed and the way their cushioning system is set up. So if you are looking to run on a surface that closely mimics outside conditions (not like concrete surfaces of course!), this is the tread you need to get. Precor has the best overall warranty with 10 years on all parts. You are looking at spending 4-5K on this Precor line
Landice is the company that first started manufacturing treads over 40 years ago in Randolph NJ. They have a very comfortable running surface and some really cool consoles to choose from, their Executive is the Mercedes of the line, you can also get a 15" LCD attachment with a built in DVD player. This is basically a commercial tread in residential form relative to the belt, motor, rollers, heavy duty aluminum frame, and heavy duty fly wheel. There are two frames to choose from, the L7 and the L8. The L7 has a 58 x 20" running surface and the L8 has a 63 x 22" running surface. I think the Precor line outspecs the L7 when you factor in the workout area you get, but if you want to go all out, you get the big block of the industry L8 frame. Landice also has the best warranty in the industry - Lifetime warranty on all parts. You are looking at spending mid 3 to 6k range with Landice depending on frame, console, and belt combination (standard or ortho)
You can't go wrong with either one of these companies, they are doing quite well financially and are the best name brands in the fitness industry. There are no special electrical requirements for the above brands. I've tried other commercial treads like Startrac and their cushioning systems are terrible. After we finish up my Dad's project Mustang, that's when we plan on getting the treadmill. Out of all the treads I've tried and studied, Landice, especially their L8 frame, has the least amount of shake, the thing is solid as a rock, even less shake than other commercial treads I've tried. The frame is crafted in an interlocking type manner as opposed to welds in the steel based frames, thus vibration travel is significantly limited. I don't know what kind of budget we are looking at, but hopefully we can go all out and get the L8 ortho with the Executive console
I hope this helps, let me know if you have any other questions