Don't do it!
Just a warning not to buy trees online. We have bought from several online companies and have yet to have one tree live.
Though they say 18" trees, you most likely will receive something that may be 18", but looks like the switch mama used on your backside when you were a kid.
Best place we found was when someone on here recommended the nursery auction at the Chesapeake Marketplace in St. Leonard. We bought several different types of trees (20 Leyland Cypress, some weeping willows, corkscrew willows, etc.) for a total of 39 trees and spent less than $200. The cypress trees were healthy 3 ft trees and all lived. They do guarantee all the trees they sell there too.
Not sure when the next auction is, but you can check with their website,
www.chesapeakemarketplace.com/auction_calendar.htm
The next plant auction will be in the spring. They normally have 3 in the spring, with the last one being around Mother's Day. We bought 10 azaleas (1 gallon size), 14 Rhododendrons (6 gallon + size) a Jap Red Maple (3 gallon size) and 2 dogwoods (10 gallon + size) for about $200.00. Both of the dogwoods came down with the blight and died, but the grower replaced them with flowering cherries (my choice) without any problems when they had their fall auction. Everything else is growing great.