By Kevin Peachey
Personal finance reporter, BBC News
Youngsters are not always keen to leave the nest
When the children have grown up and moved away, many parents have plans for the rooms that become vacant in the family home.
But it seems that the lack of mouths to feed has ruffled the feathers of these so-called "empty nesters".
Some are turning to the internet to find interesting travellers happy to fill the space.
And a growing number are recognising the earning potential of these unused bedrooms.
Of course, the existence of lodgers is nothing new, but websites are now offering residents the chance to take in travellers more frequently and for just a few days.
Christina Spencer, 52, has four children who are grown up and have moved on.
Her house in Princes Risborough, Buckinghamshire, which she shares with her husband and two cats, has views over the Chilterns and a couple of spare rooms. It has been home for 16 years.
"I work from home, so it is nice to have someone along in the evening," she says.
She advertises a double room with a television and internet access on a website that matches visitors to spare rooms. She charges £20 a night for the room - plus £5 for an evening meal.
"It is pleasant to have somebody there, and a few extra pounds always helps - but money is not the primary motivation," she says.
A sociable visitor with a story or two to tell and who leaves the room neat and tidy is the perfect fit, she says.
While good company - rather than cash - is the stimulus for Mrs Spencer, other homeowners have found that the financial crisis means they are looking for ways close to home to make money.
Some - especially younger homeowners - who bought when it was easy to borrow 100% mortgages and jobs were safer, are now aware that renting out a room can help pay the bills.
According to Mrs Spencer, the internet has proved to be a vital tool in bringing landlord and tenant together - even for just a few nights.
Stephen Rapoport lost his City consultancy job, with a six-figure salary, during the recession and decided to turn his "bedroom hobby" into a business venture.
Tracey Emin's bed would be worth more than most
Inspired by his experience in Sydney, when he could not find a hotel room during the Olympics and ended up paying to sleep in a friend's spare room, he set up Crashpadder.com.
The website matches guests to rooms offered by "hospitable locals". It now advertises rooms in 48 countries, including £15-a-night accommodation in London.
Guests search the site for suitable accommodation, the host checks the guest's profile on the website and decides whether to accept the booking - and the Crashpadder team take 10% of the fee for matching them up.
The business - run by a team of three all aged in their 20s - is yet to make a profit, but has won some venture capital backing and, according to Mr Rapoport, is growing by 100% a month.
Far from attracting backpackers and students looking for a cheap place to stay, he says that the average guest is aged 38 and 50% of them are travelling for business.
Most, he says, want to escape "sterile, overpriced and environmentally unsound" hotel rooms, and Mr Rapoport hopes the internet generation will come to the website which is similar in design to a social networking site.
"We have plans for forums and travel guides written by our members," he explains.
Miles Quest, spokesman for the British Hospitality Association, says homestay websites are still so niche that they do not offer a great threat to hotels or guesthouses.
He says the licensed hospitality industry offers more service and more extensive facilities, which make rooms more expensive.
How many people really want strangers helping themselves from the fridge and blocking the bathroom in their own home?
Matt Hutchinson, of flatshare website spareroom.co.uk, said that the start of any year was a time when many people considered their domestic arrangements.
"Many will be thinking about getting a lodger or lodging, especially young professionals who find they have a job in one area and a property elsewhere," he says.
"Empty nesters tend to have bigger properties. Rather than downsize they want to use the space and tend to take on younger lodgers.
"They attract people who want to live a family-orientated life."
Handily for these hosts, the UK's tax rules can work in their favour.
People planning to rent out a furnished room in their main residence may be able to claim "rent-a-room" relief.
This means that no tax is payable if the gross rents for the tax year - before deducting expenses - do not exceed £4,250.
But the relief is not automatic and a declaration is still needed on a self-assessment tax return. More details are available
in this guide
There are issues to think about from the guest's point of view, in addition to the obvious consideration of personal safety.
Citizens Advice recently warned people to take greater care when searching for rooms or property online.
Some rogue landlords are requesting that tenants prove they have sufficient money for the rent or a deposit by sending a receipt from a money transfer transaction.
But this receipt would carry sufficient detail for the rogue landlord to withdraw these funds, before the prospective tenant realises that the room or property does not exist.
Finding that the bank account - as well as the nest - is empty could be a financial nightmare.