Unless it's the Viking MegaQuilter 18.8, you would technically be purchasing a midarm and not a longarm. I currently have the Pfaff 9" setup, which is identical to the Viking. I found the 9" throat space to be too small and I am currently awaiting delivery of a used Tin Lizzie 18. I will be selling my Pfaff setup, once the Tin Lizzie arrives.
I'm not certain what software you would be getting, unless you are purchasing the quilting robot, either Qbot or QuiltClever. I have the Qbot and will be transferring it to my "new to me" Tin Lizzie. If it's the 4D Qbot software, it's still usable. But it's already obsolete and will cost you aprox. $150 to upgrade to the newer 4D Quilt Design Creator software. Also, check that the Qbot itself is already upgraded to version 2.07 or higher. Otherwise, it'll be another $100 or more to upgrade that to the latest version, which adds some nice new functionality.