Orangeburg pipe disaster
1. Once you buy a place unless the bill of sale has provisions in it for what you are asking, NO DEAL. You are stuck with the house as you buy it.
2. If the pipes in the yard are more than 15 years old, unless they are cast iron, are due to go at any time. The cast iron ones are good for about 20-25 years.
3. Roots in sewer pipes are quite common especially around the joints. It doesn't take very long for trees to find the joints and start penetrating the pipes. Use either a good roto-rooter to snag them out or use one of the root disolver stuff in the pipes.
As for cost... $6000 is cheap....