See a flat at 3 pm, and again at 9

Every flat has one good hour, and the listing photos were shot in it. The light is soft, the road is empty, the water is running and nobody is arguing over a parking slot. That hour is real, and there is nothing dishonest about photographing it. The trouble is that you will not live in that one hour. You will live in the other twenty-three, and those are the ones nobody shows you.

So the cheapest, most useful thing you can do before you sign anything is to come back at a different time, on your own. Not another guided tour with the broker filling every silence, but ten quiet minutes on the street, watching. A place behaves like a different animal at three in the afternoon than it does at eleven in the morning, and different again at nine at night, and only one of those faces ever makes it into a listing.

The two visits that pay for themselves

You do not need to camp outside for a week. Two well-chosen visits catch almost everything the photos hid, because they land on the hours when a building is most likely to misbehave: the hot, thirsty middle of a weekday, and the dark, parked-up end of a night.

• Three on a weekday. The sun is full on the building, so you feel the real heat of that west-facing bedroom that looked so bright online. The evening jam is starting to build, so you learn what getting home actually costs. And run a tap while you are there, because mid-afternoon is when a tanker-fed building is most likely to have run dry, and a dry tap at 3 pm tells you more than any amenities list.
• Nine at night. Is the lane lit end to end, or is there one dark stretch between the main road and the gate that you would rather not walk alone. Where has everyone parked, and is there any room left for you. How loud is the road, the diesel generator, the street dog that will adopt your window. This is the hour that tells you whether the address is somewhere you live, or just somewhere you sleep.

While that tap is running, do the rest of the unglamorous checks nobody does on the polite tour. Run the shower and flush the loo at the same time to feel the real water pressure. Take the lift down and back up and notice how long you wait for it. Stand on the balcony and find the nearest source of noise. Open a kitchen cupboard and look for the tell-tale dark line of old damp. None of it takes five minutes, and all of it is invisible in a photograph.

Ask the people who already live there

The most valuable people on that street have no listing to protect and nothing to sell you. A neighbour on the landing, the watchman at the gate, the ironing man on the corner: give any of them two minutes and they will tell you what the brochure spent real effort hiding. Ask about the water in April and again in July, because those are two different questions. Ask which junction floods, ask what the association is actually like to deal with, ask what the last tenant left over.

This is the gap our reports are built to close, so you are not leaning on a single lucky viewing. The things the 11 am tour is designed not to show, the real water situation, the flood-prone junctions, the noise and the safety after dark, are exactly the things we measure for the whole area. Read those first, then go and run your own 3 pm test on top of them. Between the two, the flat has nowhere left to hide.

A flat shows you its face. The street shows you its habits.