Since you're not just mindlessly begging for answers, a walkthrough, answers, saves, answers, cheats, CG rips, answers, a changelog, or answers, I'll answer:
There's one wiki that actually contains most of the information you're looking for, but it's not the one on Towerfag's website--you should find it after a search or two.
Yes, there are panties in the game. When you infiltrate a Princess's castle (you need the guard to be asleep, to use sleep powder on them, or have MothP put them to sleep for you) you can find panties somewhere in their room. You can combine princess panties with special items to enjoy some unusual features.
The brothel is locked behind Qhala, the snake-woman, being an active NPC in your playthrough. Pay her about 10k after sleeping with her a few times (you can't pay all at once, I don't think) and the next time you meet she'll ask you for your input on where to set up her brothel. You can drop Princesses off there to get fucked by strangers and Qhala will pay you based on factors like their sexual skill and the preferences of the local clients. If they get too much Corruption, they basically go braindead...so if you're going to pimp them out, periodically buy them back and get them purified before that happens.
Also, in the upper-left corner of the page...beneath your profile...there's a search bar. If you open that up, there's an option to limit your search queries to the thread you're viewing. It won't solve all of your problems, but it might help in the future if you hadn't tried it already.
EDIT: Fuck it, here you go (
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