Moving Game Content From One PC User To Another

So, here’s the dealio:

I got Gmod for my steam, however I don’t own the Half-Life 2 episodes or CS Source, so errors are appearing everywhere. However, another user on my computer does own everything necessary to not see these errors. I don’t want to buy these things or download a content pack when the content I need is already on my computer, so I was wondering if there was a way to find the required content, and just copy it into my steamapps folder or something similair. If anyone needs any further info I can provide.