My 6 year old has just started piano lessons, not sure whether she will continue. A local piano store has a Celviano AP 20 that someone traded in. The store owner is asking $250. I realize its very old, but for a child beginner, would it be adequate? It seemed fine to me, but I don't play any instruments. Before I saw that, I had been thinking of getting a P-85 or a Korg Sp 170. Any insight appreciated.

Any decent keyboard with weighted hammer action keys will work. But very quickly, in less than a year you and your daughter will develop an ear for piano tone and then you will not be able to stand the artificial sound of an older Casio. The new Casios are so much better. But that is OK because you should be able to sell it for $100 and by then you will know what you really need. But as far as abilty to do the job (practice for a 6 yo beginner) it will do fine,

Offer him $200. Older digital pianos are not easy to sell

In addition to the Korg and Yamaha, there is the Casio PX130 for about the same price. Either of these three are "better".

Thanks Chris. We ended up getting it, he wouldn't budge on the price, but threw in 4 piano classes.
I figured the same, that in six months or a year, we may be able to sell it and we'll be in a better position to evaluate the various options and buy the right one for us, by then we should have done our cross-country move too! I really wanted to get the p-155 (after reading all your posts) but I just couldn't justify it right now.