I'm looking to buy a used Wii U - since I've only had the Wii (the original) since 2008. O.K. that sounds silly, but I'm just not into gaming that much.
You can probably get a Wii U for pretty cheap these days or get one from Gamestop. But Nintendo Switch is what you should be getting. Especially with smash bros releasing. You should be on of those instead
I'm not sure how many games you're eying to play, but IMO its not worth it. The Wii U lacked a lot of worth and most games are coming to Switch these days.