The first step is to retain an experienced EB-5 attorney to advise you on credible agents and acceptable and legal procedures. The USCIS and SEC regulations have to be complied with.
Migration agents are often businesses or individuals located in the investor’s home country that facilitates the process. Some may simply be the liaison between the investor and the US immigration attorney and regional center. Some may assist with the preparation of documentation. We strongly recommend retaining a US immigration attorney with experience with the EB-5 program, because the EB-5 program is a US immigration process and concerns matters of US law. Methods of payment depends on the agent, but both methods you describe are common.