Some things that make me hot are apocalyptic situations.  In a collapsed, dystopian world, a man who can provide safety, food and luxuries to a woman is in charge.  What wouldn't a woman do to escape ravenous hordes of zombies?  How grateful would she be to find a civilized master vs a sadistic gang of nomadic barbarians?  She may be a little unhappy at the cost, but still grateful that her duties are far preferable to the alternatives!  I wouldn't have to lock her, or them, up.  They would know that they could leave at any time, but it was simply unthinkable. 

 These things apply to:

Zombie Apocalypse: I would have a generator, food, walls, weapons, medicine...  Any woman wishing to stay must be obedient, or leave.  Even offering up their of-age daughters.

Oppressive Regimes: In a socialist state, the world belongs to the rich, no matter the rhetoric used to sell it to the masses!  Goods are hard to come by... reliable electricity and water, clothes, even food! The authorities are cruel, corrupt...  Life is hard!  But for the elite, life is good.  Many women would gladly trade a life of servitude for the things I could offer.

Old South Plantation: The slave girls would much rather be house slaves, than field hands!  And the field hands would resent the house slaves.  They would see her as a whore, less even than them.  Live for a house slave cast out into the fields would be cruel, and without the Master's protection, she would be used, ostracized, or even killed.  Lots of incentive to keep the Master of the house happy.

Frontiers: Mostly this is the Old West!  I'm the master of the ranch, in the middle of nowhere.  For miles and miles around are savage Indians, bandits, and desert.  But here, the poor frontier widow and/or orphan has found a new home.  This would also work out to prostitutes, like Drew Barrymore and Andi McDowell at the end of the movie "Bad Girls"!  This would also work well for shipwrecks, etc...

I'm not a sadistic man by nature. Quite the opposite.  But so many submissive and slave fantasies fall into that category, that it is hard to find servant pics that don't have S&M in them.  I like to be in control sometimes, but even in the blackmail fantasies I want the woman/women to accept their place, even enjoy it!  I want "no no no" to become "yes yes, Oh, God, please fuck me!"  and even "I love you".  I just like that the relationship is clearly defined, and that there is zero chance that they would ever leave.