Rock Walls?

A guy came to our house one evening, with a sales pitch that sounded like somebody from the cosmetic section in the department store. "You need to have rock walls between your house and the next door. It's too dangerous" said the guy. I knew there's a steep slope there but never considered it a danger. 18K for 5.5 ft (H) x 2 ft (W) and 9K for 2.75 ft x 2 ft. I wish I had that much money! I know these people in the construction are hurting for money big time, but I don't fall for scare tactics!

Our house and the one next door were built by the same owner. He should have done that if rock walls were that important. It should be a concern for whoever is going to buy the house next door because our house is on the lower lot. If the slope ever comes down, the next lot will have foundation issues, not us. Besides, we are in lava zone 2! Pele can reshape everything that gets in her way.