Please take note of this information, as if you come to me with a very poorly optimized model then that will factor into the pricing of any given commission.

For the love of everything on the entire planet, please make sure the model for whatever you are wanting put into L4D2 is WELL OPTIMIZED, that means LOW vertices/indices count, if you send me through a stupidly high poly model, don't expect it to work, the Source engine on which L4D2 runs does not support exceptionally high quality models, and 30k-40k vertices would be considered pushing/reaching the limits on a smooth experience for a mod.

If you don't know how to check whether a model has an unreasonably high poly/vertex count, then I suggest you download Blender, it will be able to import most any common file format, which you can use to view the vertex and/or poly count of your selected model.