Think about it. You already own or have equity in the home and land you are thinking of attaching an ADU to. In the greater Los Angeles area, the land cost share of total home value is 61%. And if you're thinking of investing in land to build a primary residence and an ADU, consider "permit ready" or "shovel ready" plots. They'll cost more up front but will allow you to bypass a lot of the pre-construction hassles.