MUN conferences organized at University/College level are often sponsored by the host school. The school benefits in many ways from hosting one MUN conference. First of all, it is good for reputation of the institution, because it brings young and smart people together to engage in intellectual discussions that improve the quality of the education. Secondly, bringing new people to the school grounds enriches student life. In addition, bringing High school students gives them an opportunity to experience the atmosphere that might be the key point in deciding to attend that school. All these factors listed are good arguments that you can use in writing a proposal to your school or university to support your conference.
Once again, it is difficult to start a good, well-organized MUN conference. However, it is even more difficult to make it sustainable and an annual event that happens on the campus. In that case, support of your school is crucial in creating an environment in which the conference is organized on high level every year, but where university as a sponsor benefits together with its student body.