I also have an older home and we had to repair our sewer line. It was clay pipe which had broken in a few spots and had major root intrusion. Thankfully there's some newer technology that makes it significantly cheaper in the right circumstances -- instead of digging up your street connection and laying in new pipe they can blow an epoxy-soaked liner into your existing pipe, then run a curing light through it. It ended up being less than 40% of the cost of replacement and works just as well.