Catch fish
To catch fish, rest by a river, stream, or lake.
Infinite Money
If you are in town at the beginning of your journey, and you go to the stables, you know already that you can buy oxen. Oxen tend to cost from 11-12 dollars an animal. This exploit involves trading the oxen away for more money than you bought them for. Here is the most efficient way to do it.
Step 1: Buy 4-5 oxen. (The more oxen you buy, the higher chance it is that you can "fool" the computer and make a profit, but if you buy more than 5, than you'll make less money than you could. The stable will never run out of oxen.)
Step 2: Enter the trading screen, and look for dollars.
Step 3: Once you have found dollars, scroll down to see how much they have. (Remember, they have to have a greater amount of money than you spent to buy the oxen, or you wont make a profit.)
Step 4: Trade the oxen away for the maximum amount possible, while still making a profit. (The maximum amount a villager can have is 100 dollars, which can only be attained with 5 oxen. If you find one of these people, you will make 45 dollars, which was about $1500 during the time period.)
Step 5: Repeat until you have enough money! (If you are trying to get an amount of 90 dollars or higher, then you might get a refusal. Just hit the "haggle" button a few times, and they should accept your offer.)
More money
Go to a livery stable and buy four to five oxen. Then, go to trade and find someone who will trade money for your oxen. Trade the oxen for as much money as possible, but more than what you paid for them. Keep in mind that oxen differ in price depending on what location you are in. Keep trading the oxen for more money until the desired amount of money is received.