In general I agree with Evita. Certainly it is never too late to learn to play piano; true, you won't be a teen-aged prodigy playing Liszt -- but if you wanted to badly enough, by the time you were 40 you could be as good as you could possibly be, and a virtuoso!
An inexpensive keyboard is probably the best way to go right at the moment -- but with one very important warning: it absolutely must be touch sensitive; that is, the volume of the note played must, absolutely must, vary with how hard the key is depressed. If that isn't true, while the keyboard might possibly be useful for learning to play harpsichord, it is useless for playing piano. A related comment is that if you find you enjoy piano, you will outgrow a simple keyboard very very fast; you should be prepared for that.
As to how long per day to practice? A trivial seeming answer would be "as long as you want". I would expect a casual piano student would probably play an hour or so; a more serious player might well play several hours -- perhaps even as much as eight. But they would divide the practice up into say two hour blocks, and so something else in between. At least that is what I recall from the dim recesses of the past...
I heartily second the idea of finding a teacher as soon as you find that you enjoy it. It is very easy to develope some rather bad habits -- and amazingly hard to break them once they are ingrained. And a teacher can help a lot.
Topic: The newest beginner is here and needs some help