Create a perpendicular line to a stream segment and plot elevation profile

I am trying to create a python-addin button such that when I click on a stream it will create a perpendicular line to the stream at that point (or if by some error I click very close to the stream it will snap to the stream). I want to be able to specify the length of the line.Once it has created the line as a shape-file, it should then interpolate shape(elevation) from a DEM(Lidar) and plot the elevation profile.My intention is to be able to use GIS to get an idea of the width to depth ratio of a stream before ground truthing and I want to do this with just one click of a mouse button using ArcGIS.I have very little background on coding and this is my first time doing this.If any one out there have done something similar and can help me I will appreciate.

Thanks