If the machine is in good working condition and all of the knobs, levers, and gears are in good shape, it can be worth anywhere from $100 to $500. However, if the machine is in poor condition, it may only be worth $50 to $100.
Additionally, the value of the machine also depends on the year it was manufactured.
Earlier Singer machines are more valuable than later models, simply because they are older and more rare. A Singer Model 99 from the early 1900s could be worth up to $1,000, while a Singer Model 99 from the 1950s may only be worth $100-$500.