To determine how much money Victor owes at the beginning of January, we need to evaluate the function \( f(x) = -35x + 2500 \) at \( x = 0 \) (which represents the beginning of January).
Substituting \( x = 0 \) into the function:
\[ f(0) = -35(0) + 2500 \]
This simplifies to:
\[ f(0) = 0 + 2500 = 2500 \]
Therefore, at the beginning of January, Victor owes $2500.