j.trevor123,
I have to tell you true, I shoot five different ML's,own seven and have given two away as gifts.
Cost: I do not believe you or your friend would do wrong/or be the least dissapointed if you purchased a H&R/NEF Huntsman or Sidekick inline MuzzleLoader,regardless of the price. If you feel better by spendind more money,then I would recommenend a T/C Encore 209x50.
All of the above are U.S.A. made and the T/C has a Green Mountain barrel which will give you results that you would be happy with,like the H&R/NEF's. All above have removable breech plugs for easy/simple straight through cleaning (no bolts,etc to fool with :grin: )
If you prefer the more traditional,side locks, then I would personally recommend a T/C Hawken or Renegade with Green Mountain barrels. High quality for the money. Easy to clean once you get the hang of it,....and I actually enjoy it.
Caliber: I would recommend .50 cal as it is "middle road" and scads of projectiles and accessories are readily available everywhere! If choosing the T/C sidelocks,then .54 cal should also be considered,and you have a choice of barrel twists ( slow ) for round ball - to - (fast) for sabots.
Bottom line: If I was starting out, not sure how I was going to take to all this muzzleloading stuff, ....not wanting to spend $500 if it ends up sitting in a gun chest or back of closet,......I would buy a wood/blue Huntsman or Sidekick. You will love it, and never regret the purchase.
If you end up, like so many of us, eventually getting other ML's,..I would bet that getting rid/or selling of your H&R/NEF would not be a consideration.
Best of luck and bottom line,.....enjoy whatever you get and have fun shooting. :grin: