Yes. An honest estimate is better than waiting for certainty that may never arrive.
Use a rounded figure, label it clearly and choose whether it is a low, likely or high estimate. For a cost you are worried about, the higher estimate may be the safer one to test.
Keep uncertainty visible
- Use descriptions such as “Power, likely” or “Freelance income, low”.
- Do not quietly choose the number that makes the scenario work.
- Update the estimate when you learn something new.
Worth knowing: The point is not to prove a possibility. It is to learn what would need to be true.