Is it legal to close a doorway of a SFR to turn it into two units

[Jin Zhang]

Hi everyone, 

I have a naive question and could not find a good answer by googling. I am wondering if I could close a doorway and turn a SFR into two units and rent them to two different groups? Is there any legal consequences associated with long term rental, mid term rental, and short term rental? Any input would be greatly appreciated!

Thanks,

Jin