This is a simple, straightforward walk-in scam.
You arrive at her place.
She asks for the fee up fron. This is not unusual as many escorts have been at the receiving end of punters not paying after services have been delivered.
You hand over your hard earned dosh.
She may then ask you to busy yourself getting undressed or helping yourself to a drink while she puts the money in a safe place and makes herself comfortable.
Then, to your surprise a man walks in claiming to be her husband (could be her boyfriend, maybe ever the landlord!).
He will play the role out by asking for an explanation. He will typically threaten but offer you an easy way to get out of there; which, of course, you take without hesitation. You leave as fast as you can - minus your money, of course!