Welcome.
If you have not read this post you may find it useful.
Do you want to play a Piano or Keyboard? That is the question my Teacher asked when I took up playing keys after years with a guitar and bass. He qualified it by stating, there is a difference in how I teach you and in how you will develop. Piano. At its most basic level LH plays the Bass...
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If you have access to a music store you will find it useful to go there and try as many sub $700 digital pianos as you can.
I have played the S1000 and whilst it is a very neat keyboard I did find its action not as good as equivalent Yamaha or Roland models, but that said for your budget a compromise or two is likely.
In addition to the Casio that Scott quoted do check out the Yamaha models where you should find the Yamaha NP 32 on budget, the drawback with this model is that it has 76 keys.
Alesis also produce a DP that get good reviews, full 88 keys, hammer action and c$250.
Slightly over budget by $20 is a Roland Go Piano, full sized keys in a compact light weight body, 61 keys and a pretty good action at its price point but it is not hammer action, more synth action which would be good for the other inbuilt instrument voices.
You may also wish to look at second hand units on Craigs List, Ebay etc or even as at local music stores about trade ins or ex demo units.
Good luck