The qualification which you required for this job is a bachelor's degree from an accredited higher school. The area of specialization in degree is immaterial. You have to gain experience in the fields of security industry by working as an entry level job. You need several years of experience as the internal consultant for any security company to become a security consultant. You can gain experience as a security guard for any private company. Go on working hard. Work at the same place at least for three years continuously. There are a few professionals who strongly require a degree holder. If you want to get selected, in absence of a degree you require strong experience which is more than eight year's. This experience will compensate for your lesser education.
Look at an accredited program which provides you the certification of a recognized industry which is related with the field of security consultant. There are institutions which offer you the tandem certificate which can be helpful to become a private investigator. In this you can learn more about the things which are needed for the certificate from the website of Professional Security Consultants, an International Association.