Maybe I'm missing the point here, but why is it reasonable to think that a single mother with a low income should be able to afford to live in San Mateo?
San Mateo is expensive. Very expensive. Outside of direct market distortions like subsidized low income housing, it will always be too expensive for many people to live there. As many challenges as she faces in moving, she'll face more trying to raise a child in a garage.
Speaking as a once single mom with an extensive technical resume, finding a job can be next to impossible. Regardless, living in the city increases the chance.
B) She says in the video that she makes good money.
C) Our communities do better with more income/etc diversity (http://www.urban.org/publications/411955.html).