Before purchasing a cap and ball revolver, ask yourself honestly how well you maintain your modern revolvers.
Too many folks purchase cap and ball revolvers, thinking that they're cool and all, then neglect proper cleaning as too much work. Some are turned off by the slow loading process.
I've seen dozens of cap and ball guns in pawn shops, yard sales and gun shows with rusted bores and chambers because they were fired and never cleaned. And I've probably run across a dozen guys through the decades that said they bought one, then gave up cleaning it. "Just too much bother," is a common complaint.
Unless you are committed to cleaning the cap and ball revolver within no more than two days of firing it -- and sooner in particularly humid places -- I'd suggest you forsake getting one.
Yes, you can get a stainless steel Remington pattern, and that will resist rust, but much of the reason for cleaning is also to remove all the fouling created by black powder and its substitutes. That fouling hinders moving parts, causing them to drag. Black powder fouling is also mildly abrasive.
Black powder guns are not like modern ones, which can be cleaned days, weeks or months later without damage to the steel (depending upon the environment). They require extra care and commitment to maintenance.
If you're not up to that, buy a .22 pistol. It's probably the most benign cartridge made.