How long does it take to fix a collapsed Sewer line?

My son called last week and said his stool was backing up in tub He went and got a sewer snake and a rodder snake tried to unclog it but nothing happened. So Fought it all week. They live in a Duplex. And the Old people next door Kept using their stool and tub So all that mess came into our sons place. Now he has called the Damn Landlord everyday. And nothing So finally got the Plumber there at 6 p.m. last night. And he could not get the line unclogged. So they had Rotto Rutter out today and he said the Sewer Line has collapsed from the house to the Septic tank. So everything being used in coming into our sons place. The carpets are a mess. The walls are wet. Water everywhere. How long should it take for them to replace the sewer lines? Then Who is responsible for the Clean Up Our Son or the Stupid Landlord. Here this all started Friday night and here it is Tuesday and still a bigger mess then it was.