Jake,
Welcome to the sport of muzzleloading. You didn't mention what you plan on hunting, so I will assume it is deer. First check you local regulations. Every state is a bit different with what they will and won' allow. Caliber, sights and ignition systems are the primary things to check on.
Once you know what is legal I would get something in the range of a .45 to .54 caliber for deer. .50 calibers are the most popular and offer the widest selection of guns, projectiles and powder.
Twist rate of the gun is also important. Fast twists (1:32) and faster are meant to shoot conicals and sabots. 1:48 twist is an middle ground twist and normally can handle conicals, sabots and patch and ball if you are willing to work on your load a bit. The really slow twists (1:60) and slower are meant to shoot patch and ball. All are very effective on game, sabots typically give you the most range.
Traditional vs. In-line sytle gun is really a personal choice. Don't believe that just because it looks modern that it will shoot better than a tradtional gun, and don't listen to anyone who says traditional cap locks are harder to shoot than an in-line. Don't get a flintlock however if it is your first gun (unless a flintlock is required by law). They do require a bit more skill to shoot.
As for the gun you show. It will most likely work as a beginner's gun. Most of the really cheap ML have decent barrels, which result in decent accuracey, but skimp on the other components. If you get the gun don't expect it to last for years and years without problems. But if $$ are a concern, and you don't want to invest a lot because you are not sure if its for you it may be a good way to go. If you decide ML shooting is something you are going to stick with plan on getting a better gun.
I've got some good articles on my site that go into more detail about selecting a ML you may want to browse over and check it out.
BTW if you hunt is quickly approaching - you may want to wait until next years hunt. You should spend a good amount of time at the range- shooting from different positions and at different distances getting to know you gun before the hunt. A couple of rounds the night before will make for a frustating hunt, when you miss, or spend too much time fumbling with equipment trying to load the gun, or even worse wounding an animal becuase YOU didn't take the time to practice before the hunt.
cjc