The census forms are coming in a few weeks. There will be ten questions and none have anything to do with income. No one will come to your door if you fill it out and mail it in on time with no errors.
The ACS is done annually, and is separate from the Census, but run by the Census Bureau. They changed the fine this year to $5,000 from $100 if you don't fill it out. This is the part where they ask you about income, etc. Each year approximately 3 million housing unit addresses in the United States and Puerto Rico are selected.
The American Community Survey (ACS) began full implementation of housing unit address in 2005. Since 2005, the ACS interviews samples of housing units in all counties in the United States (including the District of Columbia) and in all of the municipalities in Puerto Rico.
It is interesting to note that the census from 1870 asked for value of the house and value of the 'estate' of the main person in the house. It also asked about country of origin and native language. I have census copies from from my genealogy research. The census reports are available online after 75 years.