Following her father's passing in 2024, real estate agent Shalini Karnani Bonjour relocated her mother from Michigan to California to live nearer to her and the rest of the family.

"My husband and I felt uneasy with her living so distant, particularly regarding her everyday requirements," Bonjour, age 50, shared with Business Insider.

Later that year the family purchased a residence featuring ample backyard space for an accessory dwelling unit intended for her mother. Construction on the 1,100-square-foot ADU began in 2025. What was projected as a six-week effort has extended over several months and exceeded the anticipated budget by thousands of dollars.

"Managing the entire process has proven demanding due to the numerous elements involved," Bonjour noted. "One must balance affordability, neighbor relations, and schedule adherence. I can only envision the strain for those lacking familiarity with these steps, as it represents a major commitment."

Bonjour highlights five significant lessons from the experience, covering contractor selection and preparation for unforeseen expenses.

A poor contractor choice can determine project success or failure

Bonjour initially believed she had selected an appropriate architect who would design the ADU and oversee permitting plus construction. That individual failed to deliver on those commitments.

She described engaging the incorrect professional as among the largest errors in the undertaking. After interviewing roughly 10 builders she located a replacement, yet issues from the prior architect have complicated the build.

"Observing my builder interpret the original plans resembles forcing mismatched components together," she remarked. "It amounts to working from another person's blueprint."

Mastering local permitting and building regulations proves vital

Each municipality maintains distinct ADU requirements, with some proving more intricate than others.

In her Coachella Valley area Bonjour needed approvals covering the roof, electrical systems, plumbing, HVAC, and solar installation.

"The municipality applied strict standards to solar," Bonjour explained. "The initial electrical reviews passed, yet the third review required solar panels. Securing solar in this desert setting constitutes a separate task, including research into suitable providers and options."

Construction can strain personal relationships

While awaiting completion the family shares the primary residence, which has created difficulties especially around kitchen use.

"My mother enjoys cooking, making her own kitchen essential," she said. "During meal preparation she noted it would differ once she had her own space. The situation carries mixed emotions, yet her completed kitchen should shift her perspective."

Work has also disrupted the neighborhood. An outdated transformer requires replacement before the ADU connects to power, involving excavation of driveways including those of two neighbors.

"Neighbors endured driveway closures for over a week," she added. "My contractor and I aim to minimize disruption by selecting efficient crews. The neighbors have responded with understanding."

Budget management requires careful attention

The family allocated $480,000 for the ADU, reserving $100,000 as a contingency.

"As a realtor who advises thorough questioning, I dislike surprises," Bonjour said. "A contingency provides buffer funds one hopes to avoid using. Anyone undertaking construction, whether large or small, should plan similarly."

Additional expenses such as new contractors, an upgraded electrical panel, and solar panels depleted the reserve. These costs have affected daily decisions including travel and main-home improvements.

"I would have structured the allocation differently," she reflected. "Early planning with suitable experts would have reduced complications and delays. Upgrades to the primary home must wait, which is frustrating but instructive."

Extend patience to oneself throughout the learning curve

Bonjour acknowledges she would approach decisions differently if repeating the process.

"As a professional I expect high standards of inquiry and preparation," she said. "I value positive ties with builders and suppliers. At times I feel I should have anticipated problems, which creates internal conflict."

She continues to practice self-compassion and views the ADU project as worthwhile overall.

"We recognize proximity for Mom benefits the family," she concluded. "We have gained insights as homeowners, realtors, children, and parents planning for the future."