Participants are to make their own accommodation arrangements, reservations and payments. You will find a range of variously priced places to stay in Helsinki. There is a hostel on Suomenlinna with a number of beds in group rooms. You will need to bring a sleeping bag. Sheets are provided. Accommodation is €30, and breakfast €7,90. You can make reservations for this accommodation through the seminar organisers and pay separately.
You can also find inexpensive accommodation here:
http://www.eurohostel.eu
https://www.omenahotels.com/sv/
http://www.eurohostel.eu
Or you can check out middle-priced accommodation here:
http://www.hotelhelka.com/?lang=sv
http://www.hotelarthur.fi/sv/