Have a plumber come out and have a inspection done on it ie they will run a push camera down the line and they will be able to tell you if there is any issues ie cracked pipe offset joints etc that would be a problem in the future. That will cost depending on who you get $2-500. It will be cheaper in the long run to know what’s there. Also being a row home depending on how it’s built if your house connection is on street side you may only be responsible for 5’ of sewer line before the county or city take over if it’s in the alleyway it’s typically done from the cleanout or so many feet. Myself included do not deal with those type of insurance companies due to the fact that they want it done as cheaply as possible to the point of just wanting a joint fixed when the whole lines trashed and have actually tried to hassle me over the cost of pipe. Also easy insurance don’t dump grease down the drain and say no to flushable wipes.