Here is a very interesting document on Margin from TD Ameritrade:
https://www.tdameritrade.com/retail-en_us/resources/pdf/AMTD086.pdfIt is clear from "Margin Requirements" section on page 4 that per regulation the margin loan cannot exceed 50% for opening a position, which again amounts to leverage=2.
However, the next page talks about "Maintenance Margin", which is set to 30% for sensible assets. I guess that means after initially purchasing an asset at 50% margin, one can maintain the asset at only 30% the margin.
I am a bit confused though about when does the Margin requirement go from initial to maintenance? Anyone knows?
