The sex shop is a random find.. I'm not sure if it depends on rep, dignity or morale though. The easiest way to unlock is via the maid path.
The red light district content currently ends with the hooker bringing you inside one of the rooms. Gotta wait 'til it gets updated.
I found coke from dancing at the club, there's a girl who gives you Raul's card and that unlocks another section of the club, but that content also ends very quickly. I haven't found out how to consistently get coke, though.
I haven't figured out how to have sex with Henry for a rent reduction. The sign on his door always says that he'll be back soon, so, yeah no clue.
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When I go to the loan shark and can't repay my debt, it's basically a game over since there's no way to get out of that scene.
DETAILED GUIDE TO UNLOCKING THE HENRY SCENES, MILD SPOILERS FOLLOW:
For the Henry event, you need to be persistent. Whenever you are in your apartment with nothing to do, visit Henry. At some point of time, you WILL trigger a scene which states something like you hear noises coming from inside. That is the part where a new character named Bibi is introduced. After that, again, you have to be persistent and visit bibi, mostly on sundays. A trigger will occur and she'll let you in. There you need to hear out how she gets the rent so cheap.
After that, again, visit henry and once you hit the triggering scene( it's a very obvious scene, you'll know when you do), choose the submissive route. Most importantly create a save at this VERY POINT. because i guarantee you'll make a wrong choice, i know i did, lol!
You'll know you have selected the right choice when a rather......explicit image follow up after your choice (the text will read something like he tries to insert his finger into your mouth, and you gotta let him to progress, obviously!).
And that's that! everytime you have to pay rent now, visit henry and you'll get the option to 'perform favors to reduce rent' or something like that.
PS: Depending upon your stats, you'll unlock more and better actions you can perform for lowering the rent. You'll only start with a few basics ones like making out with him or letting him feel you up. As you become more....slutty....you get better options!
PPS : every encounter you have with Henry before unlocking his scenes, you need to keep on choosing innocent and submissive answer. for eg, if faced with a ques from henry like, "i hope you don't think what me and bibi are doing is wrong( or something like that, can't remember right now)", you gotta select the choice that says no, you don't see anything wrong.
(the above scenario was an example not a real scene, though you most definitely will have one such encounter on similar lines.)
Continue this way and you'll be making good progress in unlocking Henry quickly!