Main features to look for in keyboards
1) Full size keys, not “mini” keys. This is crucial.
2) “Touch sensitive” keys. So dynamics can be played with varied finger pressure.
3) The ability to record so the student can playback their own performance.
4) “Weighted keys” (as opposed to “semi-weighted” or “synth action”). Generally only available on the largest, full size keyboards.
Some recommendations
Casio CT-S200 – Bare minimum. It’s not touch sensitive, which means there’s no way to practice dynamic control. It also can’t record and doesn’t have weighted keys.
Casio CT-S1 – This is touch sensitive and records, but doesn’t have weighted keys. If taking private lessons or practicing a lot, a full size keyboard with 88 weighted-keys is important, but in a pinch this keyboard could be adequate for roughly the first year of study.
Yamaha P71 (AKA P45) – There is a big price increase here, but this is the next step up, with 88 weighted keys. It can’t record, but a keyboard like this would generally be adequate for a couple years of private lessons. If a student really takes off they might need a decent piano before too long. Here’s a guide to keyboards better suited for private lessons.
Premium keyboards
As keyboards go up in price from here, their keys tend to slowly improve, getting closer to the feel and control of a real acoustic piano. Brands to look for are Yamaha, Kawai, Casio, and Roland. Just keep in mind, to get really close to the feel of a good acoustic piano, you’ll need to spend thousands of dollars. It’s possible to find a good used acoustic piano for the same or less. Decent acoustic pianos can sometimes be found for free. Here’s a guide to finding a free or inexpensive piano.
Keyboard stands
Unless you have a low table for the keyboard, a stand is important. Some keyboards come with stands, but some stands don’t actually go low enough for a kid sitting down. There are many on the market, but this “Hamzer” X-style stand is decent at a reasonable price. For full size weighted-key keyboards, a more sturdy stand is highly recommended. Look for more sturdy X-style stands, or better yet Z-style, or table-style stands.