For cheap accomodation check the following links:

Pension Lechner
Cheap pension in der city centre of Salzburg, only a 3 minutes walk to the afterparty!
www.pensionlechner.at

Pension Jahn
Next to the afterparty!
www.pension-jahn.at

JUFA Gästehaus
Cheap hostel near the city centre
www.jufa.at