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Here is the Saving Asset Pack from the RPG Course. Free for all to use.

If you are using Unreal, there is also:

1. The Epic Games created content: https://www.unrealengine.com/marketplace/en-US/profile/Epic+Games
2. The Permentantly Free collection: https://www.unrealengine.com/marketplace/en-US/assets?tag=4906

If you use an MIT license, there's nothing that stops you from building off that for a larger project. You don't have to release the larger project.

Also, we have a course for this very purpose! https://www.gamedev.tv/p/git-smart-course/?coupon_code=GAMEJAM_OFFER

The key to not stepping on each other's toes is to not be working on the same files at the same time. Divide up the work and have a seperate scene file each as scene files are impossible to merge.