The quid pro quo is simple: stay for free in a stranger's home while they do the same in yours, so freeing up your budget for travel and expenses.
House swapping has been around for 50 years, but now the web has raised the roof. "The internet lets members swiftly search home types and engage in correspondence," says Caroline Connolly of the HomeLink internet home-exchange agency, which has over 14,000 members in 50 countries - including 1,600 in the UK. Last year, its business rose by 25 per cent.
With most agencies - other established companies include Intervac and Home Base - you simply register your details and pay a membership fee, usually around £100 a year.
Post pictures and details of your own home and location on the site, and then you can browse the list of potential swappers. The information available should help you find a good match. If you have a large family, for example, you'll probably want a house with plenty of rooms and toys.
And don't worry if you only have a small London flat, compared to their Florida condo; location is just as important.
But before you agree a swap, it's vital to get to know your future house guests - via email first, then by telephone.
You'll have to agree a written contract together - a fixed sum for phone and utility bills, say - and feel relaxed about who's coming to stay. Agencies don't take references but monitor members and follow up negative feedback. HomeLink has an "exchange evaluation form" where swappers rate experiences, and a complaints procedure for unhappy partici- pants. It operates on a "two strikes and you're out" basis.
"There are the occasional accidents [such as breakages], but those would happen even if you were in your own home," says Ms Connolly. People who choose to trust others, she adds, tend to be trustworthy themselves - leaving their host's home exactly as they found it.
To be on the safe side, inform your home insurer of your swapping plans. The people staying in your property should be classified as guests, so any outside theft will be covered by your existing policy. Some insurers may even look favour- ably on your home being occupied while you're away.
Accidental breakages, however, are not usually covered.
To include car use in the exchange, add the other family to your licence as temporary additional drivers. Check that your insurer accepts a driving licence from their country of origin; if not, an international permit is needed, says Frances Browning of Churchill.
Travel cover can also be useful against cancellation if you or the swapper falls ill. Again, check with your insurer: not all treat staying in private accommodation as a holiday, and in that case won't pay for a claim.
Finally, lock up valuables, compile a guide to your home and its appliances, and leave a list of emergency numbers.
Margaret and Ron Fox, a retired couple from Kent, used three consecutive house swaps as a way of seeing Australia on a recent trip.
"This took a lot of organising," says Mrs Fox, "especially trying to find people wanting to exchange at the same time.
"But home swapping means you can stay in the community and enjoy far more flexibility than you get in a hotel."
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