I do have ties to this city, although I am not closed to the idea of relocating, it depends on few factors like where would I be required to relocate, is this offer going to be based on my willingness to relocate and whether the move is going to be for a certain period of time or is it going to be on a permanent basis. Will the company assist in relocation, etc.; I will also have to discuss it with my family before making a decision.
Notes: Generally, you should avoid giving a blunt ‘no’ without investigation as in most cases, the Employer is only interested in knowing your flexibility, and relocation may not be required. If the employment offer is based your willingness to relocate, then it is something you can discuss with your employer. It is better to take the interview to ‘offer’ stage, wherever possible.
Trap alert: No blunt single word answers.