Immigration matters are usually handled on a flat fee basis. The costs he is referring to probably refer to the USCIS filing fees and consular fees. As for his actual fee, it is rather on the high side. My fees for the same type of service are about 1/2 of that and I explain what the various costs are upfront. I also set up a payment plan for my clients and given an additional discount to FreeForum members. I would be happy to discuss the process and the timelines.
Furthermore, unless her daughter is under the age of 21, it will take a lot more than 12-18 months to get her to the US even after the mother is a US citizen.
Please let me know if you have any additional questions or how I can be of further assistance to you in this matter.
Lana
Immigration Attorney