I'd add that Russia is VERY big. It's rather misleading to put all russian people in a very narrow category.
Yes, there are criminal regions in most big cities. But there are a lot of peaceful regions too.
I haven't encountered 'crime in action' in my whole life.
I seriously doubt that there is absolutely no crime in Finland.
Quote from 'crime and safety report':
Visitors should exercise the same common sense security practices as would be used when visiting any large city in the United States. Visitors traveling to Helsinki during the summer months should exercise increased security awareness when transiting the airport, walking in crowded downtown areas, or using public transportation. Professional pick-pockets from other neighboring countries come to Helsinki to target unsuspecting tourists, who have let down their guard and thereby become soft targets of opportunity. During the late evening hours, travelers are advised to remain vigilant when in proximity of the downtown train station area and the Kaisaniemi Park. Occasional assaults do occur in these areas.
So I guess it's the same as in every other big city - downtown is more or less safe and outskirts are more or less dangerous.
I don't know why russian are buying lands in Finland. I haven't heard about any kind of hype about this.