I was in your situation, but was lucky enough to find a nice Casio WK-1200 (with stand) at an estate auction for $15. It has a 200 built in sounds, 100 rhythm sets, and it's own speakers, which helped me to get started with it, but are no longer used (much). It has MIDI out and in and velocity-sensitive keys are what I use now and with a few PreSonus and Native Instruments instruments software chunks, I can do more than what I figured on initially. Oh, it needed a MIDI to USB converter, called a Uno from M-audio for about $40, bringing the total to $55.
While I'll never be offered professional work as a pianist, based on this experience, I've never spent $15 more wisely. Maybe it's time to go sale-ing (as in garage sale-ing)?
With these ears, how could I ever scuba dive?