Thanks for the replies. I plan to use it for commuting to work mainly (looking for a close job to minimize commuting costs, but don’t think I can bike there). I’ll look into certified used cars.
And I won’t be paying sales tax (and I don’t think I need to pay registration, but not sure).
I’ll look more at the list of cars MMM recommends and see what I slightly used vehicles cost.
An electric car would likely have the cheapest operating costs for your use case. Look into Nissan LEAF, Kia Soul EV, and Volkswagen e-Golf. These are all easily available in your price range in barely used condition. There are several other electric options too like the BMW i3 (if you want to be fancy, tires are expensive though), Mercedes B-Drive (which no one has ever heard of), Toyota RAV4 EV (if you want a small SUV), Ford Focus EV (if you must own American), Fiat 500e (if you want people to know you have a quirky personality), etc.
If for some reason an electric car won't cut it (e.g. you need to take longer trips or you don't have a place to charge it) look into the most efficient hybrid you can get your hands on. This will probably be the newest Prius in your price range, but there are a ton of options.
Even if you aren't paying the initial registration costs I'd be surprised if you were not going to have to cover the annual registration. Depending on your state and value of the vehicle this can be hundreds of dollars per year. Just a heads up.
The list of specific car recommendations on the MMM blog is very out of date. The general concepts are still sound though.