I'll break things down into 3 sections here, any bugs encountered so far (only found one in the current build), general feedback/review on what's currently available, and a "wishlist" for the final product:

Bug:

>after reaching the end of the available content I have to close out of the game to do another run/new game. I start, fill in name/choose starting girl, and immediately get the "you have reached the end of available content" notice.

Feedback/Review:

>Overall I enjoy what's available. It's simple and fun, but I can see it requiring some brain power if the difficulty is escalated past where the demo ends.

>I'd like to see the game automatically return to the "selection" screen after placing characters in a room. Small thing, but I think it would help the flow. (I'm not super familiar with Renpy, so hopefully that's not a big adjustment to make.)

>Including a small character bio in the Workers tab (species, a sentence or two describing their personality, maybe B-W-H measurements) I personally think would really go a long way towards connecting me further with the characters. 

>I realize this is a demo build, so this may be something planned/not available publicly, but there should probably be a more distinct punishment for ending a week in the red.

"Wishlist:"

>I'd love to see an android version. This is exactly the kind of game I enjoy playing around with on my phone in bed before passing out for the night.

>Expanded cast. You've got a an awesome cast of characters, I hope more of them appear in the final game. ^^ 

>Outfits. I realize art is expensive and takes time, but I would love to see alternate outfits for the workers, either as level up rewards or as purchases in the shop.

>Not exactly a "wishlist" item, but I'm super curious about the unlockable storylines ^^

Closing thoughts:

Seems like a great start! For all the emphasis you've put on this being a demo/trial build, it seems really stable, and I'm excited to see more content! Just my opinion, but I can see this being a great "long term" game that gets updated over time and helps draw more people into your brand. Looking forward to more! 

another small bug I discovered, P.K.'s CG is still blacked out in the "extras" tab on the title menu even after unblocking it multiple times in game.

I'll add to this:

Nice little brothel manager, nice art. Just from their portraits, I'd like to know their traits and stories, eg shopkeeperchan.
Meaningfull upgrades other than just another room, and seeing steap increasing monthly costs additionally to the investment cost adds some deeper level of investment strategy. I find that more enjoyable than the typical debtpayoff with willinilly increasing rates.

What I'd like improvement on: 
Adding girls to customers to rooms is repetitive and much clicking. As OP said, maybe automatic return after you add one couple to one room helps, or having smaller room icons (without clean information maybe) in the matching window. So you should go to room window to clean them, but you could ignore that for fast matchmaking.

An upgrade that cleans rooms between customers (might be impolemented but not found)

Some character depth, various reactions to the potions (probaply planned, when you state their flavorprofile), reactions from the shopkeeper, etc.

I don't know if your current model of "earn xp to unlock customer service cg" can compete with other brothelsims, where you can add infinite pictures and maybe unlock picture sets (positions) or player interactions. On the other hand, art is time consuming. Fleeting imagery can be found anywhere on the internet, a working game framing that is IMHO far more important.