If you are buying a pre existing home with cast iron pipe and your inspector tells you the bathrooms are draining slowly, it is worth your time and money to have the sewer pipes inspected. It’s typically $200-300 here in Texas to have a plumber run a camera down the lines so you can see the condition of the pipes.
Cast iron pipes don’t last forever. Eventually they will wear down and crumble. This video shows all of the different types of issues you can have with your cast iron from tree roots growing through, cracks and separation of the pipes. If the pipe is running near a slab this can cause even bigger issues. If there is a leak in the pipe, that will affect the foundation as well.
I always tell my clients it’s well worth the tiny investment of $250 to make sure you don’t have a $5,000 to $15,000 problem right after you purchase your home. If you found this page because you’re debating whether to hire a plumber for this, do it.