Who can prepare a Millers Trust? Does it have to be an lawyer? Should a banker prepare the trust?

Anyone can write up a trust BUT, to do it correctly, specifically for this type, is not a good idea. Do you know what this trust is for and how it can be funded?

A Miller Trust (or "Special Needs Trust") is "protect the assets of, individuals with physical, psychiatric, or intellectual disabilities, and still allow such persons to be qualified for and receive governmental health care benefits".

You really need to hire an attorney to do one. If a banker tried to do one, she or he would be practicing law without a license, a crime in most places.