Should I set my tank up ahead of time

[JodanOrNoDan]

I would. I wouldn't get a tank though, for an adult I'd get one of these since they're cheaper and hold humidity better:
http://www.lowes.com/pd/Hefty-100-Qu...g-Lid/50150118

Add a UTH + thermostat for heat, some substrate, hides, digital thermometer/hygrometer, temp gun, and water bowls, and you're done.

For a baby just get a smaller tub.

I agree with bcr. Tubs are just easier. When you use a tank you tend to turn a low maintenance pet and turn it into a high one. If your prize form over function though a tank can work but I definitely would set it up early.