Building More Than Allowed

[Vivienne Chen]

Hi, I'm very new to residential development. I notice that city's regulations often limit how much a developer can build on his property. However, I saw in my community that some housing development doesn't seem to match the regulations mandated by the city. I'm wondering how developers can go about building more units than allowed by development standard on a land. Where should I go for more information before I speak to an architect. My research has brought me to density bonus for low income housings. But, the community I'm referring to doesn't seem to cater to low income housings. 

Any ideas, advice, guidance would be appreciated. Thank you.