Casio makes some tremendous keyboards these days. The Privia line is across the board excellent and can be found used for $250 or less.

Adding my vote for never ever touching an “el cheapo” instrument. A junk keyboard and guitar made me think I disliked those instruments as a younger person, and it makes me sad when I see kids struggling with instruments that I can’t make sound good with years of experience.

Digital pianos around the $500 mark are pretty good these days.

Seconded, Yamaha, Kawai and Roland all make gear in that price range that is nothing short of incredible in terms of quality and sound. Besides the fact that they don't need tuning like an acoustic would and which tends to add up over time.

Just putting in a vote for my Casio Privia PX-S1000.

Ah yes, they are also pretty good, I tried one at a music store here in nl but forgot about it. Definitely worth a mention.

Very few people can afford to blow $500 on something they don't know if they'll commit on or not.

Get secondhand for $100-150.

If you've got the space, you'll find that you can get a real upright for free in most cities in the world. Sure, it won't be the best instrument ever, but if you ask around you'll find someone chucking one out.

After a few tunings, you might wish you bought the keyboard.

Yes. We were told that we should move our piano away from the outside wall next to a window because the temperature and moisture fluctuations were causing it to go out of tune.

We're in an old house and there isn't a piano-sized space in our living room that doesn't have a window, door, or HVAC intake/vent.

That's a very important point, tunings will rapidly exceed the value of any 'cheap' piano. And typically the cheaper they are the worse they will keep tune, though there are exceptions to that rule.

I can recommend Entropy Tuner, which is a great piece of software to help you tune a piano properly.