Get the MC influence up to 45 - 50 for all of the girls complete all of the required hints available by clicking on the book icon in the top Right corner once it says next step requires 45+ influence and gang introduction for all three girls,
go to the lounge/living room when the mom/Landlady icon is there in the evening and it should trigger automatically.
If your after the Ntr content don't pay the debt mentioned 2 times then go to the lounge/living room mid afternoon when Mom/ Landlady is there and it should trigger.
If you require gang influence to trigger events simply tank your influence by skipping time for a couple of days after the introduction and the gang and Deons influence will go up. Be warned it becomes very grindy getting your influence back up after you do this.