Which of the following factors affects an investor's return on investment the least?

The individual credit score is the factor that affects an investor's return on investment the least compared to the other options listed. While an individual's credit score can influence the terms and conditions of financing, such as mortgage rates and the ability to obtain loans, its direct impact on an investment's overall performance is less significant than factors like property location, market trends, and interest rates.

Property location is critical because it determines the property's desirability, demand, and potential for appreciation. Market trends reflect the broader economic environment and can heavily influence property values and rental rates, directly affecting an investor's profits. Interest rates play a crucial role in the cost of borrowing—higher interest rates can significantly increase financing costs, which diminishes overall returns.

In contrast, while a credit score may determine what type of financing is available and at what cost, an investor may still invest in properties that experience favorable market conditions or are in prime locations, regardless of their individual credit score. Therefore, the individual credit score is relatively less impactful on the overall return on investment when compared to the other factors.