Characters and animations
https://www.mixamo
and
https://www.assetstore.unity3d
Also the Unity Asset store has tons of free and cheap assets:
NOTE While it takes some converting understanding, and you need a basic knowledge of Unity, it’s not that hard to get content, pull it directly from the Assets folder, open the FBX in Maya, scale it up (typically by 100), fix UV map overlap, export FBX, import into Unreal. Many of the companies that sell on the Unity Asset store have their own sites where you can purchase directly from them and they generally offer the raw FBX.