Sounds like your reasons for getting into muzzleloading are the same as mine were three years ago, mainly to take advantage of the extended season. That being the case, you could justifiably go with the bare minimum expense for the time you will be using the muzzleloader. It all really depends on you, whether you want to go with something high quality or start out with a "starter" gun. Kind of like someone who decides to learn how to play guitar, does he start with a student guitar, or does he drop the cash for something of higher quality right away. Note that someone's entry level gun may well be a lifetime gun for another.

Me, I was in a situation where I was flipping a shotgun I was not using so I had a little more cash to burn at the onset. As such, I was able to get a gun that I feel no need to upgrade. This was fortunate for me because as some have already noted, my simple plan of using my ML just for the muzzleloading season has pretty much evolved to using it for the entire season.