California- the tax bill is higher than the rent

[Mary Jay]

HI guys,

we bought this property in California in 2019, we rented it to section 8 person.

3 years later we received a bill saying we owe 11K in taxes (plus 4K in penalty, of course). 

The problem is we did not rent the property the whole year so we only received in rent 9K in 2019...

How could taxes be higher than the rent we received?

The letter came from this organization:

www.ftb.ca.gov

they want us to pay through this website: officialpayments.com

or call this phone number:
1-800-272-9829

1) Is it even a legit company?

2) We have been paying property taxes. I guess we missed a rental tax (we live outside California)

3) Is it an income tax? Or is it a tax on a rental income? Seems like its too much of a tax for a 9K rental income for one year

4) how does the tax on the rental income is calculated? lets say we make 30K in rent per year (in 2020, in 2021, in 2022)

Thank you