I checked with the government labour dept., you have to pay for the air ticket (one way) and the helper's salary (if you do not give her one month notice, then you have to pay one month additional). As for the immigration, visa, medical check, you have to pay the agent if you hire a new one through them. Yet, if you change to another agent, than you have to pay the agency fee (a few thousands I believe). Therefore, I guess your best bet is to stick with the same agent as they will find you a helper without charging you extra agency fee, unless you are not satisfied with this agent.