ADU in a Gated SFH Community - Huntington Beach

[John Cusick]

I own an about 3,000 s.f. house in a gated SFH community in Huntington Beach, CA, and am considering building an ADU of about 900 s.f. on the same lot. Based on my preliminary research, it appears as though I should not have any problem getting an ADU approved by the HOA and the City. However, since this is the first time I am looking into this issue, I'd appreciate any advice as to what problems I may run into getting the project approved. Also, how would building an ADU affect the value and marketability of the house? I am trying to avoid any unintended consequences . . . for example, may adding an ADU in a fairly upscale gated SFH community decrease the desirability of the house for prospective buyers when I am ready to sell? Any other pitfalls I should consider?

Also, what should I budget for this project for the architect/engineer/permits?  What should I budget per SF for construction?

Thank you!