Hardware does not come cheap, and if you pay low prices for the lower end hardware, you will get the lower end quality. A decent keyboard may set you back around at least $1,000 which may be over the budget for many beginner musicians. If you are just starting out I would advise purchasing a MIDI controller keyboard.
What is a MIDI controller keyboard?
It looks like a regular keyboard or synthesizer but it how no on board sounds, therefore light and inexpensive.
If it has no on board sounds, what use is it?
They work by triggering sounds by sending out MIDI signals directly to your computer or via Audio interface. Your desktop or laptop DAW can interpret these signals and convert them to sounds as if you are playing a real piano. Your DAW would use a plugin called a VST which can emulate various sounds. If you have a good Piano VST then you could play the piano through your controller keyboard. A Rhodes VST would allow you to play the classic electric piano sound.
You can even get controller keyboards with weighted keys like a real piano for you realistic feel although most MIDI controllers are none to semi-weighted.
You could pay $100 – $200 for a decent controller keyboard and then around $50 – $100 for a good VST which can sound just a good a any hardware. The thing you will need to consider is the extra luggage if you plan to perform live. The keyboard itself is lighter then a real synthesizer however you would always need to carry your laptop and audio interface around too.
There is also the latency (delay) to think about if you have a slower machines. The latency is the time is takes from when you press a key till you heard a sound from the speakers. A good value is said to be 10ms or less. Anything more than that would be difficult is you are trying to play with accurate timing. This can be overcome with a faster processor and better audio interface. Also if you are not using many samples at the same time things can be tweaked to get lower latency.
Also remember that controller keyboards cannot send audio, they only send MIDI signal and can be connected via a MIDI cable or USB. Once a performance is recorded is can then be exported as audio e.g. WAV or MP3.
See below for some good industry standard MIDI controller keyboards.