Ok this one I have mastered. If you have a bounty in Lemoyne you can lure the bounty hunters to a bridge in the northern region of Lemoyne as indicated on this map:
Stay on the west end. Grab your Lancaster repeater. They all come over the bridge on horseback and give you ample time to pluck them off as they ride virtually single file over the bridge into their deaths. If you kill a horse, loot the saddlebags as well. Sometimes you get gold nuggets from them. The hunters usually always have watches and belt buckles from silver to platinum, plus they carry cash.
I usually ride the road on this map where the player is from one bridge to the other that crosses through the word "Water" on the map. Eventually bounty hunters spawn and I rush to the closest bridge and do this all over again on both. I almost never take even a single hit, rarely have to use dead eye, and the game never stops giving you goods like this. After 4 or 5 spawns they start dropping tonics and no more rings or buckles. When that happens, ride back to the fence. I use the one in the west because I'm not wanted there but there's also one a little north on the coast. Each run I net some $150 to $200 including the money the guys have on them when I loot them.
If you're not using dead eye, this free firing builds your shooting experience, and also lowers your honor bar every time you loot someone. I personally don't care that I lose the honor. It just pays way too well.
I did this for a few hours, upgraded everything I can in camp, paid off all other bounties I had on the map and leave Lemoyne with a huge bounty just so they will keep sending guys after me. Anymore, money is no longer a concern for me in the game.
Don't forget, if you're heading to town to buy bullets, remember to snag a 3 star elk or something before heading in. You'll get something like $12 from the butcher for the perfect corpse. You can hold one big corpse on your horse, but what seems like infinity pelts, and 2 slots to hang birds on the sides. Plus, you can fit a ton of small critters in your bag. I always murder and skin any animal with a 3 star rating. Use the varmint rifle for small things like rabbits. For pigs, deer, etc, use a rolling block rifle and aim for the head.
Using these tactics, you will never need to worry about money again.
UPDATE
I should also mention I have reached new levels of depravity. Just for the challenge, I ride the streets of lemoyne and fire off some revolver rounds into the sky so the witnesses will alert the police. When they start to chase me, I charge straight up the map to the bridge by the E in water and continue to slaughter them as they arrive. When you do this, the police will come after you for maybe 5 or 6 spawns back to back so you don't even have to wait for the bounty hunters to find you again. Bounty hunters can be several minutes in between spawns. The police just keep coming. Let the bodies pile up. You eventually get good enough to loot a few in between waves but don't prioritize that. The bodies will wait for you. Remember, it's just a game, so don't feel bad about shooting down all their horses as well. As a bonus, their bodies rot and you eventually have one nightmare of a bridge covered in skeletons for your amusement. Any time a stranger is passing by, shoot them in the leg or something. They run off and notify more police and the heat begins again. You can keep this up as long as you have the ammo and the space to stash the goods. Check your butcher in your camp. He can make a satchel that doubles your loot storage (or more). It is definitely worth doing the hunting chores needed to get that made.
Know your limits though. Don't forget that even in the pure chaos of battle you can quickly open your satchel and drink down some miracle tonic or chewing tobacco to refill your deadeye instantly. Nothing will anger you more than taking down a hundred men only to lose all that loot because you got sloppy.
Always keep in mind that the citizens and creatures in the Red Dead world have no memories and they all respawn like they're stuck in groundhog day. You might feel a sensation of remorse when you start shooting down horses or strangers simply to trigger a massive attack. But as soon as you no longer want to test your warrior limits you can pay off the bounty and it will be as if it never happened. There really is no consequence to farming this way, so do as you must. With the doubled satchel, I can pull in some $400 + each run. In this game that's practically retirement money.
//imgur.com/a/QIX2uQQ
Animal and fish habitats.
There is a link to known sell prices of stuff but I lost it. Hopefully someone else still has it.
Deer and especially Buck are very good to go for. Well, anything that dispenses Venison.
Cougars are worth an extreme amount but are a pain to hunt and there seems to just be one per spawn so meh.
Really though the best way to make money hunting is don't be picky. Just kill, kill, kill, collect as much as you can, try to not be super far from a butcher, and kill on the way to the butcher for some extra stuff. Don't be picky about star quality either.
Bring a varmint rifle, a lasso and a bolt action rifle and you're pretty much set.
Rarer birds can be worth a lot. West, northwest and north of Saint Denis is great for alligators, various high value birds and boars.
if you kill very small birds that just go straight into your inventory, make sure you go into your satchel and select "break down" on them.