Activate Hotspot Month to Month

[Wheresatom]

I've been thinking about getting a T-Mobile hotspot so I can test firsthand what their reception is like in the places I frequent. I want to just buy a hotspot outright from someone and activate it for one month. How does that work? Would I then buy a SIM from them and pick a plan? I have had a Verizon phone since I got my first in 2004 so I'm really not sure how it works on some of the other carriers.

Thanks form the help.