Most hotels the agencies use know exactly what's going on and don't care or are paid off.
In regards to condos most agencies tell you to use the code they give you to enter, and to not just follow somebody else through the building entrance, as that may trigger the concierge's concern. They also usually tell you to not knock on the condo unit door, as that may cause the neighbours to complain to the concierge.
Long story short, if you enter the condo front door code and just walk in once it automatically unlocks the door, the concierge will not likely give you a second look.
The one and only exception to that is many years ago when I was visiting an sp at a condo used often by that agency. The police had been tipped off that the agency was supposedly using underage girls, even though it wasn't. As it happened the sp was entering the condo front entrance at the same time I was, as I was her first client of the day. So we went up together. A few moments after we entered the unit, as she had a key, there was a knock at the door. We didn't answer it. Then another loud knock, with the police announcing their presence. We still didn't answer hoping they would just go away. Anyways the concierge had given them a key to the unit and they let themselves in. Thankfully the lady and I had just gotten out of separate showers and weren't even in the same room when the police entered. They told me they were looking for underage, but my sp had ID to show them she was in her mid-twenties. They took my name and birthdate, told me "You are playing a dangerous game...", and then let me leave. I never heard another word about it. (I had already given the money to the sp up front, so the agency credited me for a full free session.) And the agency stopped using that condo from that point on. I had visited that condo, using the same agency, many times previously without incident, but once the police got involved I guess the concierge had no choice but to cooperate.