"How long has it been since the boiler was last serviced?"
While that might not seem like the most important question to ask at a first viewing, it's the one thing homeowners regret the most, after they land themselves the keys.
It's followed by 'what's the broadband speed?' and 'is the roof intact?'
A further two thirds said they wished they'd asked someone 'independent' for a second opinion, too.
Joe Gordon at First Direct, said: "Good advice is sometimes ignored, but when it comes to buying a property, listening to anyone who's already been through that experience can be a vital source of advice to housing market novices.
"When buying my first house I took some friends back with me for a second viewing, and I'm so glad I did. They'd already bought a home themselves, and were great at asking the questions that just wouldn't have occurred to me as a first-time buyer."
The survey of 2,000 homebuyers around the UK also found that almost one in three (30%) bought their last home after just one viewing, while more than one in five (22%) discovered botched DIY jobs after they had moved in.
Here are First Direct's 10 questions to get in early, before you lock in any kind of offer.
1. Ask to see the boiler and its servicing history
One in four homebuyers told First Direct they regretted not checking the condition of their property's boiler and its servicing history. Given it can easily cost upwards of £2,000 to install a new system, it's worth asking those questions.
2. Examine interior and exterior walls for cracks or damp
Not every crack is a sign of subsidence or other structural issues, but that doesn't mean they should be ignored.
If you're unable to tell whether it's a superficial blemish or potentially something more serious, ask an expert. More than a quarter (27%) of buyers under 35 wish they had done just that.
3. Inspect the electrical systems
More than a third (36%) of homeowners wish they'd taken more notice of the electrical systems in their home before they bought it. Just four out of ten bothered to inspect sockets and switches, let alone the wiring and circuit breakers. If in doubt, ask an electrician to check for you.
4. Visit the property at different times of the day
More than four in every ten homeowners say checking the street and surrounding neighbourhood at different times of the day is crucial.
A peaceful idyll at 7pm could be a noisy nightmare during rush hour or at school drop-off and pick-up times.
5. Find out what the broadband speed's like
Don't assume all urban areas have speedy and reliable internet access, or all rural properties are in blackspots.
Assuming you can't live your life without the internet (who can?), find out what the typical speed is for the area and what type of broadband is installed.
Almost half of homeowners surveyed admitted it wasn't something they'd checked, and almost a third of those said they wish they had.
6. Don't be rushed into an offer
Take your time before submitting your offer to the vendors.
Even in a fast-moving market, almost half (48%) of all homebuyers warn that you should do your homework and weigh up the pros and cons, and that it is better to miss out than make a six-figure mistake you could regret for years.
7. Check the central heating system
If the property has central heating, make sure the radiators work as they should. Even if it's the height of summer, and the heating's switched off, ask for it to be switched on so you can check.
Almost half (49%) of homeowners admitted they didn't do that the last time they bought a property.
8. Check the condition of the roof
More than half (51%) of all homebuyers admitted they didn't check the roof of the last property they bought.
The British weather can cause havoc with a roof. The odd chipped or broken tile, or loose flashing, may not be a big problem, but water getting inside the building could well be.
9. Get quotes or estimates for repairs early
Two thirds of homeowners told researchers they'd incurred additional costs after moving in, due to unexpected repairs, botched DIY jobs by the previous owners or renovation work being more expensive than they thought.
So look for all those possible jobs and get builders to quote.
10. Take an independent person to a viewing
If you've found your dream home, family and friends won't want to burst your bubble by telling you the harsh truth.
It doesn't have to be a builder or architect – just someone who'll point out the faults or ask the difficult questions.
Just over two thirds of homebuyers took someone else to at least one viewing for a second opinion.