Accommodation in Sweden: scams you should look out for

What are the most common scams in Sweden?
Organized scams are not so common in Sweden but overpriced rent is becoming very common.

What are the red flags to look out for when scanning through adverts?
When a room is for rent and the rent is too low and it says only for ladies then ladies should be aware from someone who wants more than a roommate.
If a private person offers a first-hand contract most probably a scam.
If the owner says you can rent but can't be registered in the address that means either owner has no right to rent or taking money from the government. 

Is there a list of registered or accredited landlords or real estate agencies in Sweden?
Yes, if the landlord is a company they are in the list. You can check it in the webbsite of the "kommun" you want to live in. But it's allmost impossible to rent a place right away from accredited landlords. Private persons who rent out second-hand are not in those lists.

What authorities should be sought should one come across an accommodation scam?
It depends on the scam. If you allready are living in the particular accommodation you should first contact "Hyresgästföreningen" https://www.hyresgastforeningen.se/
which is not an authority but they are the main recognized organisation which taking care of everything what has to do with rental accomodation.
But if it is a real scam and you never signed a contract and never recieved keys then you should contact the police but the police always has staff shortages so they only take your complain and nothing notably will happen so the best thing is that make sure not to be scammed.

When it comes to Buying if you do it through a real estate agent you have nothing to worry.