Many times underground pipes burst due to age/decay, normal wear and tear, shifting clays/foundations, freezing, or because of a tree root. 

It's always best to try to see if you can work with your existing buyers and get to the root of the problem if they cannot pay on time.

My name is Pete and I am currently an investor St Louis, MO.My family has lots of roots in Minnesota as my wife is from the cities and I also went to college there.Anyway I saw you posted a while back about wholesaleing in the cities.I am in search of a renovation/remodel project around the Richfield/Bloomington area.Looking for something 3-4 bedroom and 2-3 bathroom and it has to have a decent size garage.To be most honest I want to find a place to fix up to BRRR and have a place that is close to the airport to park one of my cars up there so when I come in town to see family I don’t have to rent a car every time.

Ground is still warm so roots have a chance to grow. 

Not a bad idea for the AM to also be skimming/reviewing the maintenance tickets in the system for patterns of un-adressed root cause resolutions.

I also don't know if there were signs that there was already a problem from the tree roots when the neighbor purchased the property.

If they ran a camera first and observed a broken, bellied, or root filled section, then I would be digging, but not before.What were the specific issues with the three year old toilets?

I believe that OP has a broker that they are working under, but it doesn't appear that Bert can hold a license anymore.Something else, the root of the problem that I've seen appears to be with OP but Morris has certainly covered for them.

The area is pretty big and there will be lots of large roots from a huge pine tree in the middle of the yard, which is why I was hesitant.

If the system is under sized (to many bedrooms) the tank will need to get pumped more frequently.The other thing to consider are roots from trees and bushes they have a way of getting into (clogging) septic lines.I would try and find out when the last time the tank was pumped, and when they recommend pumping.