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.)