On bigger Poway lots in Green Valley, Garden Road and Twin Peaks, the sewer line often runs a long way to the street, and a longer line has more joints and more places to fail. Shifting ground, roots and age open those joints, crack sections and leave low spots where water sits. The first job is finding where along that run the trouble is.
The contractor's inspection shows how far out the problem is. One bad joint can often be fixed on its own. A cracked section under a driveway or a long yard is a section repair. If the line is failing along its whole length, replacement is on the table, and lining or trenchless replacement can keep a long run from turning into a long trench. For homes on septic, the contractor looks at the line to the tank as well.
You see what the inspection found, hear the options and tradeoffs in plain English, and get a recommendation. Then it's your decision, and a licensed contractor does the work when you say go.