2. This one is hard to quantify. Senses (like hearing) are so subjective. There's definitely a sound to it, but it's not obnoxious. When I am on phone calls, the other folks can hear it, but they say it sounds like the sound of a washing machine in the distance. https://www.dropbox.com/s/diutjkdudu5edq1/treadmill_sound.m4... I recorded about 25 seconds of my walking. When I play it back, I can barely hear it in the recording… so I'm not sure how useful that'll be. Note the position of my mic on the left side of my desk, relative to where the treadmill is positioned.
3. Yes. LifeSpan Fitness stuff is certainly not the cheapest. I wanted to go for durability, and I was willing to pay the price for it. I have had this treadmill for 4 years and use it 5 days a week, minimum. I keep the belt lubricated. I would do some research on brands/models that are in your budget, and focus on the durability factor. The brand doesn't matter. You just want to keep moving and have a treadmill that will last you a long time.
I have an email in my profile. If you have any more questions, don't hesitate to reach out to me! I'm also happy to hop on a video call with you, if you want to listen for yourself.