Fancy being lord of the manor in a Scottish country house, complete with its own hunting forest, walled garden and loch – for £60 a week, all bills included? Or how about living in a cemetery lodge or vicarage for the same price, or in the double domes of a Victorian observatory in Wirral, with a view across the Mersey (telescope not included)?

For 30-year-old care worker Lorna Sankey, a 14th-century charterhouse (a Carthusian monastery) near Coventry has been home for the last year. “It’s quite nice living among priceless medieval murals,” she says, climbing the oak-panelled staircase, where leaded windows look out on to a rambling garden, the site of the former monks’ cells. “I only pay £225 a month, so it means I can work part-time – and we have all this amazing space.”

Sankey and her housemates join a growing number of property guardians choosing to inhabit quirky vacant buildings up and down the country, taking temporary refuge from the overheated rental market. For a knock-down fee they receive a licence to occupy the premises, with an obligation to look after the building. But crucially they have none of the conventional rights of a tenant, so can be easily moved on when the owner wants the property back. “It’s not a very secure way of living,” says Sankey. “We could be kicked out with two weeks’ notice, so you always have to have a plan B.”

Originally developed in the Netherlands as a form of “anti-squatting” to secure buildings against uninvited guests, guardianship is a rapidly growing part of the UK property security industry, with around 20 private companies offering space for up to 10,000 guardians. Most are concentrated in London, where a plethora of redundant council-owned buildings awaiting demolition or refurbishment provide alternative interim bases for those happy to put up with basic facilities and short-notice periods – or what the company websites describe as “adventurous living”.

James Eagle, a 29-year old architecture student, lived in a former council youth centre in south London for two years with 16 others, paying £220 a month – a fraction of the local rent. “It was a great way to meet like-minded people when I first moved to London,” he says. “You end up in some really interesting spaces. My friends have lived in churches, schools and an old care home, complete with an industrial-sized kitchen and stairlifts – which proved useful after a night out.”

While guardianship companies’ websites brim with romantic Victoriana – crumbling castles and cosy pubs – where you actually end up is something of a lottery. The holy grail properties, such as 100 Piccadilly, managed by Live-in Guardians, where you can reside in the heart of Mayfair beneath crystal chandeliers for £100 a week, are few and far between. A rundown school or ailing office block is closer to the norm.

Since the recession, there has been a 40–50% increase in guardian properties, with local authority buildings making up the bulk. Guardianship giant Camelot, which houses 10,000 people across Europe, boasts about having had every London borough on its client list. “Councils are shutting down buildings everywhere they can to save money,” says Tony Brennan, the company’s regional manager for the north. “Only 20% of our properties are residential, but we’re dealing with a growing number of housing estate “decants”. It would cost a fortune to secure these estates against squatters, but we provide the service for a very low management fee.”

“It’s a win-win-win situation,” agrees Zoë Oakes of Ad Hoc, one of the largest guardianship companies in the country, with eight regional offices and around 1,500 guardians on its books. “The property owner pays next to nothing for security, the guardian pays much less than normal rent, and we make money.”

Put in these terms, it may well seem that everyone’s a winner. But the fact that these outfits are increasingly making use of empty council properties for commercial gain has not gone unnoticed among housing campaigners.

“They are parasites on the housing crisis,” says Rueben Taylor of Squatters’ Action for Secure Homes. “The guardianship industry legitimises keeping buildings empty and makes it a profitable thing to do. It also represents the legalisation of a two-tiered system of tenants’ rights – those who can afford to have rights and those who can’t.”

A standard licence agreement specifies that potential guardians must be in employment and not have children, pets or a criminal record. They must agree to sleep in the property at least five nights a week, not have gatherings of more than two people, and be subject to random unannounced inspections. Breach of terms – including leaving fire doors open, smoking or use of candles – are punished with fines or termination of the contract.

“It’s essentially a form of unpaid labour,” says housing researcher Gloria Dawson. “Guardians guarantee that the value of the property is retained, but have none of the security of a tenancy. Because the licence is not defined as housing, it’s not subject to the usual regulation – such as deposit protection, multiple occupancy regs and standard notice periods. Guardians are put in an automatically insecure position, with no redress to the property owner.”

For councils dealing with vast estate renewal projects on uncertain time frames, the idea of cheap passive security – along with the impression that buildings are lived in, not boarded up – is clearly an attractive one. But there is a real danger that guardianship companies are effectively beginning to act as social housing providers, operating relatively unchecked.

“We have a lot of people in desperate need of accommodation,” says Julian Fulbrook, the Labour councillor responsible for housing in Camden. “Guardians allow us to get the maximum possible use out of council flats that are scheduled for rehabilitation or rebuild, which we can’t offer standard minimum tenancies for. It’s a very flexible and adaptable system – we don’t want it to be over-regulated.”

One of the chief benefits, in Fulbrook’s eyes, is that the guardians are vetted, ensuring they are “decent, honest people”, so they’re not going to be the “nightmare neighbours from hell”.

“They are incredibly resilient homesteaders,” he adds. “We had a terrible block of flats, very dilapidated and full of asbestos, with these troglodyte bedsits, literally below ground. No one would want to live in them, but the guardians went in and made a nice little roost.”

Such anecdotes fit with other tales of dwelling in decrepit surroundings, with guardians sleeping up to 12 to a room, using temporary bathrooms with no ventilation and, in central London, paying close to market rent for the pleasure.

“Property guardianship is a symptom of quite how low our expectations of private rental housing have become, and what people are prepared to accept,” says Dawson. “The vetting process and licence agreement also reflects an alarming trend across the board of the idea that you have to ‘deserve’ housing. You increasingly have to prove you’re worthy of being housed, whatever sector you’re in.”

Unlike registered housing providers, guardianship companies are a strange hybrid byproduct of the security industry that have operated in the shadows for too long, critics argue. But with their growing visibility, the legal basis of their licence agreements is coming under increasing scrutiny.

“These contracts are very careful to state ‘this is not a tenancy’,” says Giles Peaker, partner in the housing team at Anthony Gold solicitors. “But it doesn’t matter what the document says – it’s down to what the situation is in reality. The wording tries to avoid giving exclusive occupation to the guardians, but if it were tested in the courts, the 1977 Protection from Eviction Act may still apply.”

It seems that no guardianship company has yet allowed such a case to reach court, but several claims of unlawful eviction – when locks were changed with guardians’ possessions still in the building – are said to have reached settlements before proceedings were issued.

“If word got around that these licences were not compliant with the Protection from Eviction Act, and property owners realised they could wait for four months rather than two weeks to get their building back, then there’s a problem for the business model,” says Peaker.

Beyond the legality of the licences, the increasingly accepted culture of “adventurous living” is a slippery slope for housing in general. “The most dangerous part is the glamorisation of precarity,” says Taylor. “They’re making it seem really exciting to live without any security, which means people are not willing to defend the tenants’ rights that have been historically fought for.” When it’s our only option for affordable housing, the novelty of camping in office blocks, playing a constant game of eviction roulette, may soon wear off.