One important advantage Unity has over other game engines is the Unity Asset Store. The Asset Store is an excellent resource for developers with a huge variety of free and paid 3D models, sounds, and scripts available to include in your project.
After experimenting with Blender and researching some of the expensive commercial alternatives, it quickly became apparent that I would need help building the graphical assets for RoadBall Rally. Finding suitable assets for your project is a time consuming effort that will involve lots of experimentation. To keep my project clean, I created a separate test project that I would use to import and test assets. In the end I used a number of textures and materials from Yughues who offers a large number of popular and free material packs and I purchased the Simple Town environment from Synty Studios mostly for the car models.
In my experience the texture and materials assets are a great resource for first time and indie game developers who may not have the technical or artistic ability to create their own graphical assets. I'm more reluctant to use the scripting assets in my project. In most cases it is easier to write the code myself then depend on 3rd party scripts. I also want to make sure I understand all the code in the project and that I'm not depending on 3rd party code that may be abandoned in the future.