You should familiarize yourself on US Code: Title 13, Chapter 5, Subchapter V, Section 193.
When a census worker came by last year I told her that I had sent in the form with only the legal questions answered.
She told me that if I didn't answer her questions that I could go to jail, I told her that if the federal government wanted to give me free room and board that badly that she could be my guest.
She left saying that I "would" hear from her supervisor.
No one ever came back.
I don't care what BS that they try to feed you, the census is only authorized to count the population.
You are not required to answer questions about income or whether or not you own or rent.