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
Yamaha YPT270 – Bare minimum. It’s not touch sensitive, which means there’s no way to practice dynamic control.
Donner DEK-610S – I don’t have first hand experience with this brand, but have read good things. This is touch sensitive. (You have to be careful in this price range as many keyboards with similar model numbers are not touch sensitive).
Casio CT-S1 – This is also touch sensitive. If taking private lessons or practicing a lot, a full size 88 weighted-key keyboard would be much better, but this keyboard might be adequate for roughly the first year of study.
Donner DEP-20 – There is a big price increase here, but this is the next step up for keyboards, with 88 weighted keys. Again, I haven’t tried this brand, but have read good things. Some people prefer it over the more expensive Yamaha below, which is a decent 88 weighted-key keyboard.
Yamaha P71 (AKA P45) – A keyboard like this would generally be good for at least 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 to private lesson study.
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, 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 a decent one I’ve found 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.