Note there are 2 models. One is WiFi only and the other can do both WiFi and 4G Cell Data. It looks like the dual model comes preconfigured to use a Winegard data plan. It also supports Verizon and AT&T.
It's pretty easy to go through quite a bit of cell data when using the cell network to watch cat videos or TV shows. If your intent is to use cell data as your primary way of connecting to the internet, depending on what you expect to do, you may need a large data plan.
You'd have to check with the carriers to find out how much they want to supply you with a SIM card and data plan. If you already have Verizon phones with their data plan, it may just be as simple as adding a device for $10 or $20/month and getting the SIM card. AT&T is probably similar. How much they charge for data depends on how much data you want. We spend most of the summer at a resort that has excellent WiFi with huge data allowances. So most of the year we have a 4GB data plan on our phones and MiFi device. When we head out to Elkhart next summer, I'll probably bump the data plan to 20GB for the month of June and ask DW to minimize watching videos on Facebook.
Looking at the operating manual, you have to have a bit of technical expertise to get it set up. If you're serious, you should call Winegard to see how much free support they'll provide over the phone.