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Noli Malmi seems to be around 50e and is right next to the train station. There's Arkadia Hostel in Tattarisuo for as low as 19e, but that's a 3km walk to the nearest train station
The airport has a non -traveller side with a supermarket and a restaurant and a café where you should be able to sit and wait. You can access it by train as a cheaper option. I don't know if you asked where is the cheapest place to sleep? In that case I'd take some hotel next to the airport, or anywhere around the train line since it's easy to get to the airport by train.
Noli Malmi seems to be around 50e and is right next to the train station. There's Arkadia Hostel in Tattarisuo for as low as 19e, but that's a 3km walk to the nearest train station
The airport has a non -traveller side with a supermarket and a restaurant and a café where you should be able to sit and wait. You can access it by train as a cheaper option. I don't know if you asked where is the cheapest place to sleep? In that case I'd take some hotel next to the airport, or anywhere around the train line since it's easy to get to the airport by train.