The same question has been answered here: http://www.frask.eu/questions/affordable-dutch-classes. Please refer to the second answer. For the sake of ease, I will sum it up for you now.
Via this link: https://www.nltraining.nl/cursusaanbod/nederlands-verbeteren , you can apply for a government subsidized course in Dutch for various levels depending on preference. If I'm not mistaken, you'd only need to pay a one time fee of around 50 euros, which includes the course, as well as the materials you will be using.