I have to agree, it's a great program and if you use it already and like it, you NEED it. But, if you've never used it you can get by on Photoshop alone. A lot of people here use Illustrator for the drawing stage of the profile but if you had to choose one or the other I think most everyone doing rendered profiles would choose PS. It also comes down to which program/application you're more comfortable using. So, as you're just starting, no need for Illustrator yet

It's a really great piece of software but only if you can afford it.