Building income property on existing SFR

[Grace T.]

Because home prices are so high in California, one strategy I'm considering is building on my existing SFR and essentially turn the property into a multi-family. The lot on my home is large and has room to build a "back house." I'm still at the beginning stages in terms of finding out building costs, financing it, etc. Any advice on things I should look out for, what to do, what not to do, success stories, horror stories? Looking forward to your input!