So you want to be a Mendix freelance. Ok. First of all: take the Rapid exam. It is doable after a couple of weeks of Mendix, so it will be no problem for you, and at job interviews it will prevent you having to answer the question why you are not even Rapid developer.
Landing a freelance job requires more than that though. “Advanced certificate and 3+ years of experience” is often a requirement. Investing in the 2 day training “Advanced” will help you. It will also help if you keep your hourly rate at trainee-level, and have good references that are willing to talk to your future work-provider about your past work in a positive way. Think of you being your future work-provider. What skills and experience would you want this Mendix Freelancer to have? Also: make your Mendix profile public and fill your portfolio.
All this can be replaced by you, being very good in selling yourself. Create a network, in this community, but more important at possible future employers, Mendix-partners, and potential end-users.