We had to check out of the apartment about 7 hours after check-in because there was black mold in the shower and a very bad industrial stench which gave us headaches and turned our faces red and hot, in the apartment.
After trying to buy scented candles, opening the huge windows to air the stench out (it was -5° C outside) and trying to ignore the black mold in the shower, we decided it would be safer to book a hotel last minute instead of staying in the apartment.
John was very sorry about our experience and refunded his part quickly. I don't think this is the experience of every guest who stays there, but it was not very pleasant for us.
The location of the apartment was very good and John's employee was pretty quick to answer me about these issues.