The non-holonomic behavior and the presence of dynamic singularities are only a few factors that make collision-avoidance path planning of Space Manipulators (SMs) such a hard task. Additionally, contributions in the field of motion planning of SMs often concentrate in the point-to-point strategy, with particular interest in the complex dynamics of such systems. As a criterion, collision-avoidance for space manipulators depends on a previous computed path. However, this computation still lacks robust formulations, specially in the case of free-floating manipulators. Our goal consists in creating a collision-avoiding path planner for a free-floating planar manipulator. The dynamic model is based on the Dynamically Equivalent Manipulator and the concept of Rapidly-Exploring Random Trees serves as a framework for the developed algorithm. A combination of a method that reduces the metric sensitivity with a bidirectional approach is proposed in order to achieve a solution convergence. We simulate the path planning task for a three-link planar free-floating manipulator considering the presence of an obstacle. The results are then discussed and promising directions for future works are presented.