squatting is actually called adverse possession, the requirements in virginia are:
15 years of uninterupted occupation
It looks like once you are there for three years you cannot be charged with a crime, but you don't get to keep the property.
It should be noted that i am not a lawyer and just did a quick scan of the va code. http://leg1.state.va.us/cgi-bin/legp504.exe?000+cod+8.01-236