BootsnAll Insiders

My husband & I are interested in taking the Trans-Siberian Railway (and transfering to the Trans-Mogolian Railway. Anyway, my concern is that we will be on the road prior to Russia & I have a a feeling it will be more than 3 months until we reach that point, so how should we go about Visas? From what I've read so far, everyone says you need to get it from your home country, but I don't think that will be possible in our case. What should we do?

Thank you,
Lisa