Welcome! Glad you joined us......
Well Donna beat me to the link for the Buyers guide, but will add that crawling around in and under any trailer will give you insight to how it's been cared for, what potential issues you will have. Enjoy the search process!
As far as tow capacity, you are gonna be limited. But I suggest you stay within the tow capacity and the best way to do that is, Weigh any potential purchase that way there are no surprises.
So what part of Montana are you in? Use to live by Glacier. Don't see a lot of Glass up there but they do come up for sale
on occasion. ID seems to have more as well as Oregon (the glass capitol of the country!