Cheap but decent keyboard for learning the piano at home?

Yes I know, it would be best if I took lessons and learned on a real
piano but l can't afford lessons and I don't have access to a piano,
which I also can't afford --- at least not until I get the basics
down.

Desperate here. I've wanted to learn how to play the piano for as
long as I can remember and frankly, starting on a keyboard would at
least be something. It sure beats the heck out of not doing anything!