You only have to reach the goal 1 time during the level, once it's met it counts toward the goal.

Examples:

• 1- If a goal is 5 goats, you can purchase 5 goats and then sell them. You have reached the goal and it's marked off the goal list.
• 2- If a goal is $20,000, you can make $20,000 and then purchase additional upgrades/products/animals and the $20,000 goal will be marked off the goals list.

This is generally the best way to achieve the money goals on most levels.