Margin basic number

Margin requirement  no marter you buy stock, options, futures and FX

Q:  I see initial margin $xxxxxx what is that means?

riss: You are now holding the stocks positions.
riss: They are marginable

riss: So, you need to keep some margin requirement in order to hold it
riss: equities with loan value must exceed the maint. margin

riss: For opening positiion, you need to refer to 'available funds'
riss: It equals to 'Equities w/ loan value - initial margin'

Q:  selling on margin

selling short available only if  stocks available to sell in margin account.  Cash account is not
for others selling or borrower

Fact1:  stock cound be impossible to short at any time but put option as alternative way to short