It's only a brothel if more than one person is working there either consecutively or at the same time, but if the multiple prostitutes are over a long time frame it's not likely to cause problems. If it's more than one a week/month and some random bloke is calling the shots I can see there being some interest though, especially at those rates - the folk from POCA must be drooling just reading this.
It most certainly is controlling prostitution for gain, as well as being downright creepy and weird. It would appear that the OP went out of his way to make the original ad look like an ordinary room let for an independent lady, when he's actually looking for people who will allow him to interfere in their businesses (or at least recruit for his working flat) and this is an out and out attempt to deliberately mislead our members. If I had been looking for a room to rent for work, it would have been a complete waste of my time answering this ad and I wonder how many others were taken in.
The only reason I haven't banned the OP and removed the thread is because I would rather like to hear his explanation of why he thinks this was an acceptable thing to do, rather than just being clear and honest in the first place? And reasonably promptly would be nice.