The answer depends on a number of factors, and some of your own preferences, as well as your goals as a keyboard or piano player. It’s also heavily influenced by a person’s preconceived notions about piano lessons and what they will need to do to learn piano.
Let’s start with the most important question first – why do you want to learn to play piano? Is it for your own enjoyment only? Do you want to play piano professionally someday? Do you currently own an acoustic piano and want to use a keyboard to practice late at night or in a space with very thin walls, where the piano might disturb others?
Do you currently play or would you like to play the keyboard in a band? Do you want to test out your ability to learn piano on a somewhat inexpensive keyboard first, before making the investment in a more expensive acoustic piano?
There should be a common thread in these answers should be somewhat obvious once you spend a little time thinking about your motivation for learning piano.
It’s very easy to spend as much or more on a keyboard than you would spend on an acoustic piano, but you can also find keyboards that sound and feel better than acoustic pianos. I never thought I would say this, but if I were just starting out and didn’t already love my acoustic piano as an instrument and piece of furniture, I would probably lean towards a keyboard for learning and practicing piano.
In fact, as a professional piano player, I play and practice almost exclusively on digital pianos all the time these days. And most of the time, that’s on a Yamaha CP33 Digital Stage Piano.
The “action” (feel and response of the keys) on this $1000-or-so keyboard is simply amazing, it’s relatively light at about 50 pounds, and the piano sounds are excellent. There are a number of other sounds and functions, but I honestly just use the piano sounds about 95% of the time.
As I said before, you can easily buy a used piano for less than $1000, but it will need tuning every now and then, will be affected by humidity, and will be a lot bigger and heavier than the CP33.
If you want to pay about half that much but still have a keyboard with great action and sounds, I would recommend either the Yamaha P95 or Casio Privia or CDP-100 keyboards. The action is not quite as great as the CP33, but is still very nice, and these are all very light, portable keyboards.
All of these keyboards have the full 88 keys, by the way.
Roland also makes some great digital pianos, but you will probably pay more than $1000 for them. However, if you’re serious about getting a great digital piano, you should definitely try them out before making a final decision.
These are the keyboards I’m most familiar with, and I would not recommend buying models with less than 88 keys, or non-weighted keys, because the real piano feel is just not there, and if you do want to move to piano one day, it may be a little extra work for you.