You really don’t want to make yourself depend on a 3D modeler. Free artists ready for 1-6 month commitments are few and far in between, especially anyone capable of animating. The good news is, the further you develop your project and therefore your skills, the greater your chances are of finding a dependable art collaborator.
In the meantime, use place holder art!
Just scour the web for free models. BlendSwap.com is a great place to start. Get comfortable with the jME3 asset pipeline. When you’ve got nothing that fits, use cubes. The best way to tell for sure that your game is fun is if you and others enjoy playing it in spite of lackluster visuals.