I am planning to visit a friend in Saint Petersburg soon. I'm from Germany and already obtained my tourist visa through a visa service. Last time I was in Russia (Moscow), I had to get an invitation from a service online (from Saint Petersburg) in order to get the visa, but this time the visa service made the invitation for me (although I did not receive an invitation document from them). On my visa it says it's from Moscow.
I remember that in Moscow nobody at immigration asked me about my trip or where I'm going to stay (probably because I'm a university age guy from Germany and not exactly at risk for immigrating illegally) but I'm wondering if I could run into problems if I can't produce a hotel reservation, so my question is: Am I allowed to stay at a private home with a tourist visa or could this be a problem at immigration?