@jl, Square's free magstripe reader works with older iPads (you'll probably need to update to the latest version of the iOS to install Square's Register app). You can order one directly from Square at @jl, Square's free magstripe reader works with older iPads (you'll probably need to update to the latest version of the iOS to install Square's Register app). You can order one directly from Square at https://squareup.com/help/us/en/article/5067-get-a-free-square-magstripe-reader.
I use an iPad 2 and an iPad 3 with a Square Stand (a bigger piece of hardware ideal for higher volume countertop sales). But these are the old "30-pin" iPads, and they do NOT work with the latest Stand ("lightning" connector) sold by Square. 30-pin iPads only work with the old "30-pin" Square Stands. I found a used 30-pin Stand on Craigslist. Interestingly, they are rare and seem to go for about 150% of the cost of a new "lightning" connector Stand.
To sum up, I'd tread carefully when buying an old "30-pin" Square Stand for an old iPad, but the magstripe reader is free so it can't hurt to try it out!