no bun or yan can be immediate available, if the agent refer you one, she will be terminated one and had no visa working for you. If you sign a finish contract local maid, will need at least 3 weeks for her visa to be issued. So don't hire one which can be immediate available, it is illegal. You cannot call police if she steal things from your house before her visa issued or no insurance for her during that period, too risky. You can hire local part-time maid, the salary is higher but will be more safe.
Another solution for that is to find a replacement first and wait for the new maid visa issued and then terminated the current one, the problem is you need to pay double levy for that.