Promising review: "I used this exact folding treadmill for the first two years of the pandemic, and only recently sold it because I moved and didn't feel I needed it as much anymore. (I like to run outside when I can!) If you're looking for a small yet reliable treadmill, though, I can't recommend the Xterra TR150 enough. The track is large enough to run on at 50 inches long and 16 inches wide. There's a little rack below the LCD screen that I always found useful for holding my phone or iPad to watch videos while I ran. Its speed goes up to 10 mph, and it's not overly loud while you run on it. Now, just because it's a smaller treadmill doesn't mean it's not heavy — it weighs just over 100 pounds, so you won't want to be moving it around every time you use it, even though there are wheels on the bottom to assist with transport. It's bulky enough that I suggest finding a dedicated place for it, but it certainly is movable if needed. As far as assembly, it was fairly straightforward and easy to do on my own.

Btw, you'll want to consider picking up a treadmill mat to put underneath to not only protect your floor but also prevent dust from entering the belts and mechanical parts — this is the one I used with the Xterra TR150 (the medium size) and it held up well for me over the years." —Jenae Sitzes, BuzzFeed Staff

Get it from Amazon for $393.78.