If i'm going to transport a two tiered cake intact, what kind of cake box would I use and where would I get it. I'm used to having a seperate box per layer.

I just use a cardboard box. When I get supplies shipped I save the square boxes, like 12x12, 14x14 etc. If I don't have one to fit, I go to the UPS store or Wal-Mart and buy one. Make sure to include the cost in your price. A 12x12 from UPS costs about 4 bucks. Or you could drop off the cake and take your box back with you and use it again if its clean. Make a hinge on one side so you can just slide the cake in and out, then just tape it up.

Depending on the size of the cake, I use either the File Storage boxes from office supply stores (very easy to open with the removable lids), or Home Depot sells Small, Medium, and Large heavy duty moving type boxes. All very sturdy, and cheap.. Of course I use only new boxes.

Check out the delivery system boxes by Bakery Crafts (scroll to the bottom of the page)...
http://bakerycrafts.com/Home/Items/tabid/69/SrchStr/del%20sys/Default.aspx