Ace is, of course, correct. Let me add a bit of my own opinion, if I may. In addition to errors and varieties, there is also the less lucrative, but still profitable area of direct sale of coppers. That little niche is steady, but relatively small in my area. Buyers include stackers of all types, some collectors, metal artists, and a host of others.
I keep things local. Mostly Craigslist, coin clubs, preppers, artist guilds if they have bronze foundries. As I wrote above, the market is less lucrative than errors and varieties, but it is steady. Most of these folks are not going to come looking for you. Rather you have to look for the market.
Time for coffee.