Hi
Kerri - I have a treadmill at home that is an Exerpeutic. It is rated to 400 lbs. I have a really small home and wanted a supercompact one, but it was rated only to like 250 lbs. It was less than $400. Incline options are both minimal and manually adjusted, and it only goes up to 4 miles per hour, but when I started I was walking at 2 miles per hour and adjusting up to 2.5. Now my basic pace is 2.8 mph, with several-minute bursts at 3 mph. I think it will be some time before I outgrow or outpace it. The one I have is the TF100. There is also one they make that is more compact and less expensive, and rated to 350 lbs. I do not know how tall your boyfriend is, but there were critical reviews about it because it had a shorter footprint and didn't well accommodate long strides. You are pretty tall yourself, so you might want to pay attention to that.
Mine is a bit bigger than I would like, but otherwise is exactly what I wanted and needed and was totally affordable.
If you search on amazon for a 'walking treadmill' you will find both options and perhaps some others. As long as your goal isn't running on a treadmill, they should accommodate moderate fitness walking.
