I'm a real estate agent building a $480,000 backyard home for my mom. I still made these costly mistakes.

Shalini Karnani Bonjour in her California backyard. Courtesy of Shalini Karnani Bonjour Shalini Bonjour is building a 1,100-square-foot ADU in her backyard so her mother can age in place. The project is taking longer than she expected and is going over budget.