I think you need somebody else there, preferably male, to open the door, take the money and just watch out for you, rather than potentially being alone in a room with several strange men.
I'm the male in this scenario when a friend and I organise gangbang and bukakke parties.
We get them to meet outside a pub nearby and then go there together to collect them and bring them back to the flat. That way we get them into the building quickly. Otherwise if we give the building address they tend to show up all at different times and it's not discreet having the door opening and closing that much. Too likely to attract attention from the neighbours. If it's about 5 guys we just walk them all in in one group. Or if it's closer to 10 she walks half of them in and then I bring the others in once they're inside. Just in case we do bump into a neighbour.
Also, we've found that if 20 to 30 guys click "I'm going" For one of our events. 5-10 maximum will show up. Not that we'd want 30 but just so you know these events are a timewaster magnet. And hundreds more will message us asking about the event with no intention of coming. They're just happy if a woman (or me replying on her behalf) on the internet will respond to them.
So it's a lot of work to organise but the actual events have always gone well. Guys have all behaved themselves and we've got some regulars who've been coming back to each event.
She charges about half per guy what she'd normally charge for an hour 1-1 and I take my cut but with 5-10 it's a decent amount for the duration of the event. But not so great considering all the hours it takes to promote and organise and answer messages etc