Potentially, there are two ways of using keyboards;
1. Using a keyboard to create, play and arrange live musics and pieces using "arr/acc" mode - this way sorts of automated instruments such as strings, bass, drums, etc. are played while playing.
2. Using a keyboard to play solo melodies (like what you see in a piano solo sheet) - this way no automated instruments are played.
Keyboard players of the first category usually have difficulties when jumping off playing real pianos. But players of the second one, easily go on playing a real piano after a short time.
Just consider the following noticeable differences between a keyboard (piano-mode) and a real piano:
Keyboards: Soft and light buttons to play / Pianos: Little harsh and almost very heavier buttons
Keyboards: Usually contain five octaves / Pianos: more than seven (Note: there are also keyboards with 7.25 octaves or else)
Keyboards: Pitch Shifting (Transpose shifting) enabled / Pianos: This feature is there only on some digital pianos - acoustic piano doesn't carry this feature.
Keyboards: Pitch Bending enabled (Some of them) / Pianos: You cannot bend.
Keyboards: Volume can be set as what you like / Pianos: You cannot change the volume.
Keyboards: No need to tune periodically / Pianos: You must always keep making sure if the instrument is tuned correctly.
Keyboards: Output for headsets or comprehensive set of audition studios and saloons / Pianos: Accurate microphones need to be installed.
Keyboards: Mostly support one pedal of Sustain / Pianos: It possesses two pedals.
As my final advice to you, If I were you and I did not have enough money to buy a grand piano, I would go buy a digital piano with several effects of a keyboard instead of buying a simple keyboard. Think about it!