Practicing on a keyboard?

I have an upright piano, but my mom just had babies so I have to keep
quiet a lot and pianos are loud, so I've been thinking of buying a
cheapish keyboard to practice on since I can use headphones. Is this a
good idea and worth the $150 I'd pay for the keyboard? I'm sure I'd
practice a lot more, I'm just afraid that playing on a cheap keyboard
may ruin my technique or musical ear or something. I'm a beginner, I
know very little and don't play well yet, so I haven't really
developed technique or an ear. That's why I'm so worried.

I'm considering the casio ctk-4000 because it's within my budget and
has graded keys or whatever. I've played with it at the store and it
feels good to me, not quite like a real piano, but not bad either.