I got married in May, and opted to do my own makeup. Several years ago I actually worked as a makeup artist and pondered hiring an old colleague of mine but after two trial runs on my own I went with doing it myself. However, there are plenty of makeup artists out there - although I highly suggest getting a trial if you can (most charge for it, but not all). While you mentioned you've been to mall counters for makeup I do want to say that some of those people are makeup artists who you could hire (it's where my old colleague and I met, then we both ended up doing freelance). You might find a makeup artist at a bridal show, just google searching (your city + makeup artist), finding one at a salon, or even checking on Craig's List. If you have any friends who have gotten married near where you will be, you could check with them (if their makeup looked good and held up!).
As for if you need to go to them or they come to you, it varies. Some will come to you, others have you go to them (more common if it's a salon). When I did freelance, I would go to people where ever they wanted me (although worth noting if you're getting your hair done at a salon, not a lot of salons let me go there - so I had to meet up with the bridal party elsewhere. Lots of people get ready at their hotel). I didn't charge if they were within so many miles of me,and from there I had a fee (common b/c at least 25% of my clients I had to charge for. typically I didn't have to drive more than an hour or two).
As for price... dang. It varies wildly! It depends on many factors - where you live, experience of teh person doing it, how many people you have them doing makeup for (i typically cut them a break if I was doing several people vs just the bride), etc. Most makeup artists I know charge more for teh bride (but that's b/c you want them to be more of a perfectionist with your makeup, they typically spend more time on the bride, and bride includes a trial) - most people I know charge $75-150 for a bride. Many charge more for airbrush, but some keep it the same.