Walmart would be your best bet for finding cheap horizon treadmills.
You can find reasonable treadmills at department stores like Walmart or Costco. As a Craigslist.com shopper I have seen many postings for those types of treadmills. You can also find them in local classified ads.
You can find used treadmills for sale on the auction website Ebay.
You can find cheap folding treadmills at fitness equipment selling websites such as the manufacturers website. You can also find them at walmart and sears.
To find cheap fitness equipment treadmills, one should consider looking at outlets because they generally have merchandise at reduced prices. One can find that the Sears Outlet sells treadmills at a discounted price.
You can buy inexpensive treadmills on sites like amazon, ebay, and various retail sites. You may also be able to find some for sale by owners on craigslist.
Ebay has lots of used treadmills for auction or buy it now.
Yes the normal weight limit for most treadmills is 350lb.
The best thing of searching for a treadmill is looking first at surplus. Items at surplus are cheap but will do the job. Make sure to search for treadmills that will fit in your room.
Used treadmills can be purchased online. Craigslist and eBay often have listings for used treadmills for sale.
Check out www.craigslist.org in that area for used treadmills people may be selling for cheap. You can also try www.overstock.com for great deals.
There are many websites that offer cheap new or used treadmills, such as pushpedallpull.com or fitnessblowout.com. You may also want to consider looking at craigslist or eBay for local used treadmills on sale.