I am approved for selling uncovered Puts - or "naked" Puts - which do not have a set margin requirement.
But for others who may not be approved for naked option writing, there is normally a 20%-25% requirement - in other words, one has to have that amount either in assets or cash in the brokerage, above and beyond any other margin which may already exist.
Assuming the requirement is 25%, to write a single Put option at a strike of $1200 ( $120,000 trade value ), that is $30,000
Since I do not directly short individual stock, I do not know the margin requirements if one wants to short, say, 40 TSLA shares.
For exact details, plus your particular brokerage's requirements, it would be best to contact them and ask.