Ah ok then how can I get a gun that is required for Sarah room on Thursday
The gun requires a bit of patience and, as you can see in the previous posts, it's a bit bugged, but since you're interested in the futanari prostitute, you'd be killing two birds with one stone.
I think first you should go to the gym and have a humiliating scene with Monique. She should mention that she can write down a training program for the MC.
Now that you can go out of the house, go to Monique's workplace during working hours, navigate past Elizabeth and to Monique's office. Among the talking options you should have, or eventually get, an option to ask about the training program. She should answer by giving a three days schedule: check if it comes out as a hint. If it doesn't, you might've been caught by a nasty bug.
Training in the gym outside those three days and before having talked with Monique gives you nothing.
Once you've trained the MC enough, he'll say something about being ready and the hint about the schedule should go away, so you just ignore the hint about still having to talk with Monique, spend _all_ your money on useful shit, wait for the night and go to the dark alley to get robbed.
After that, you have to talk with Trevor (I think only in the morning? It's been a while) and he will sell you an old Colt 1911 for a reasonable 350 USD.
With that, you can advance the main quest and/or go to the dark alley by night and have some payback time with the robbers and the bitchy hottie: after you clear the coast you'll be free to meet the futanari there.
Money:
I hope you like memory games.
If you have some cash (10-20 USD at least), there's a memory game on MC's own computer, in his room. Every time you play it, you earn 20 USD in zero game-time. Have the MC play it 5-10 times every day and he'll earn more than me IRL. Both the futanari prostitute and Trevor will eventually offer the MC to be a sex worker, IDK if it's lucrative, I never went that route.
There might be more ways to earn money but I don't remember them ATM.
If you're down to 0 cash, walk outside the house: in front of the door you'll find an envelope with 10 USD (repeatable once a day). Another of the many shoot-outs to "Man of the House".
With those 10 dollars, you can return to your room and play the memory game up to the desired sum.