I get a newsletter from a grower that supplies plants for companies that do interior plant design and maintenance. Here is their "blurb" on your tree:

"Keeline Wilcox is proud to bring to your attention a plant from New Zealand for your interiorscaping needs. The evergreen Corynocarpus has found a place in interiorscapes because of its ability to withstand medium light situations, making it a good substitute for the more commonly used Ficus. The upright habit of the Corynocarpus makes it ideal for creating a dense screen or divider, as well as an individual specimen.

This plant, while still relatively unknown by the interior trade, is gaining popularity throughout the United States.

Given the outstanding qualities of the Corynocarpus, Keeline Wilcox hopes you will specify this plant for your next interiorscape project."

I have no personal experience with Keeline Wilcox, but they are a large, reputable supplier. They are in CA, so I suspect that is where your nursery is ordering it from. If so, I would expect it to be in a planting mix suitable for indoor use. Looking at their price list, it appears that a one gallon can would be about 4 feet tall and a five gallon about 5 feet.

I suggest going for the smallest size. Smaller plants tend to acclimate much better to new growing conditions. And, of course, they are cheaper to buy and ship!

I hope this helps - let me know how the tree works out for you. We get all our plants from Florida since we're on the East Coast - not sure if your tree is even available here but it looks interesting!