Unless the Miroku Bess is a total write-off, $200 is a good deal.
I bought a Miroku Brown Bess a couple of years ago. The comments about the trigger guard and stock are correct. The stock is deceptively flat and straight - much more so than I expected. I would not call it a "comfortable" stock the way a good-fitting fowler or rifle can be comfortable.
When you buy a used gun, you buy the previous owner's maintenance habits with it. I believe the one I got was a reenactor's gun because when I received the gun, the previous own had left a blank charge in the bore. The seller had not checked and was surprised when I told him the gun shipped and arrived with a charged bore. Part of the bore close to the breech was rough. I believe the charge had been left in there for a long time and the bore was not always cleaned after shooting. It had one area of concern down by the breech but the rest of the bore was OK - certainly not pristine but not a drain pipe either.
What I ended up doing to solve the issue - and it's not something you'd necessarily think of when you think of bore cleaning - is to plug the touch hole and fill the bore to the top with Evaporust. The process needs to be done in a relatively warm environment because Evaporust slows to a crawl in the cold. Mine took an afternoon of Evaporust, scrub, back to Evaporust, scrub again, etc. until it came out clean. I also sent one of those cell phone endoscopes down the bore to inspect the pitted area.