A landlord must pay £40,000 after letting tenants live in disgusting and unsafe conditions.
Askar Miah, 52, admitted running an unlicensed house in multiple occupation (HMO) and breaking four health and fire safety offence to magistrates in Southampton.
He was fined £36,000 and ordered to pay £3,830 costs.
The court was told that tenants shared the seven-bedroom flat in Southampton High Street.
The fire alarm did not work, fire exits were blocked and the communal rooms and hallways were dirty.
Windows were broken and many walls had mould from damp.
Council housing inspectors found mouse droppings on a shared cooker in the kitchen.
Seven tenants were living in the squalor.
The city council has a ban on Miah letting tenants stay at the property until repairs are carried out and the flats are licensed as an HMO.
Magistrates told Miah that he a poor landlord and his failings left his tenants and neighbouring properties at risk if a fire had started.
HMO crack down
Meanwhile, Southampton City Council has launched an HMO licensing scheme requiring all shared houses in many parts of the city centre to sign up for a five-year fee starting at a discounted 240 for an HMO with three tenants.
The discount is available until the end of September 2013.
The council reckons landlords run around 7,000 shared houses in the city – with most catering for students in the neighbourhoods covered by the licensing scheme.
Councillor Warwick Payne said: “The council has exhausted all avenues available to deal with the many problems associated with some HMOs.
“Residents tell us that this is not enough. We are concerned that many residents are living in unsafe housing.
“We want to identify bad landlords and prosecute them if they fail to mend their ways.”