I am new to Drupal and have studied a bit about how it works. In order to get moving on developing our site, I was looking at purchasing premium templates that already looks good and just needs content and graphics.

When I was working on Zen Cart, I know that templates can sometimes break a site especially if they start tinkering with core codes to make some special function or if some modules conflict with what is already installed.

Is it the same way with Drupal? What is it that I need to be checking before I make a purchase? (Aside from making sure the version number is the correct one that I have right now.)

Thanks for your assistance.