IS there a way to make a hole in the terrain without needing to pay for a asset to do it.

You can use a depth mask to mask a part of the terrain and simulate a hole.

From http://wiki.unity3d.com/index.php?title=DepthMask

Put this shader on your mask mesh

 Shader "Masked/Mask" {
  
     SubShader {
         // Render the mask after regular geometry, but before masked geometry and
         // transparent things.
  
         Tags {"Queue" = "Geometry+10" }
  
         // Don't draw in the RGBA channels; just the depth buffer
  
         ColorMask 0
         ZWrite On
  
         // Do nothing specific in the pass:
  
         Pass {}
     }
 }

Then you cannot use setRenderQueue because AFAIK you cannot access built-in terrain material. You have to download built-in shader and change the render queue directly on the shader of TerrainShaders\Splats\Standard-FirstPass.shader to at least 2501. Here the line to change :

 "Queue" = "Geometry+501"

If no hole appears refresh the Base terrain material by selecting (again) "Built In Standard".