Choosing a keyboard for a beginner

by Victor
(B.C.)

I am a beginner and want to learn the keyboard, which is my interest. However, many tutors say they only teach piano so I have decided to learn piano and for this I need a keyboard to practice on. Some tutors say you need an 88 key keyboard; one music salesman said I could go with smaller number of keys. I am confused even before starting to learn.
What is my best choice of keyboard and how many keys do I need esp. if I am to practise my piano lessons?
There are many beginner level Yamahas mentioned in this site (all good) so I am not sure which is the better one.
Will appreciate your comments.