I went to the property, found the sewer was crushed by tree roots outside the house and excavated and repaired the sewer pipe in 45 minutes (NO B.S.) and the cost for materials was about $25.

I think low interest rates are really at the root of it.

Speak to a real estate agent about finding you another duplex,  Look at Zillow and Trulia to try and find a suitable new buy for your self.Keep us informed about your decision and your research because we are rooting for you.  

Use these questions to cross check previous questions and answers, to develop your gut feeling, get clarity and root out deception!

Too much shade and competition with tree roots.

Some clogged drains come from solids lodging on pipe defects like off set joints, roots, or bellies in the line.

then I just need to decide if I will dig out the roots,  or just keep cutting the new shoots until the root system dies out

Any sewer line with roots is eventually going to have roots in it again.

The flaw of your conclusion is rooted in the different stratum the FSBOs operate The paragraph above specifically mentioned it (surprise-surprise) -  The median income of FSBOs was $84,000 and for those who sold through an agent was $105,600.

I just wanted to root you on and say that's really kind of you to think of helping your Mom that way.