A used nikon d90 with 12K actuations?

Is that too low? How many actuation does a new nikon d90 have?

A new D90 will have a couple hundred right out of the box, because of testing before Nikon puts the camera on the market. 12k actations is pretty low, the D90, I believe is rated for 100, 000 actuations, but can last much longer, or shorter, depending on how well the camera was taken care of

A new D90 shouldn't have any! No such thing as too low. The lower. The better…

It's relatively low considering how old that model is. Make sure everything works perfectly before handing off your precious cash.