The issue has been highlighted in new research by mortgage broker Alexander Hall.
It found that single homebuyers in fewer than one in 10 authorities pass a mortgage affordability test.
This compares to joint homebuyers, who pass a mortgage affordability test in a massive 82% of local authorities.
Mortgage affordability
The latest research by Alexander Hall reveals how important it is for a household to have a joint income in order to get a mortgage deal.

How the housing landscape is set to shift
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The data found that only 8% of local authorities across Britain have an average house price that falls within the threshold of affordability when it comes to securing a mortgage. This is based on a single average income.
The research analysed average earnings data across each area of Britain, before looking at whether buyers had a realistic chance of climbing the ladder.
The calculations were based on a 15% deposit on the average house price, with an average income multiple of four-and-a-half times income.
Some 8% of local authorities have an average house price and mortgage loan requirement that sits within the affordability threshold of four-and-a-half times the average earnings of an individual person.
Wider regional picture
The research also found that five out of 12 regions in Britain do not have a single local authority where an individual buyer could get a mortgage based on these criteria.
These include the East Midlands, the East of England, London, the South East and the South West.
Buyers who are looking for the best chances of securing a mortgage need to head to Scotland.
The nation is ranked top in terms of mortgage eligibility, with 35% of all local authorities having an average house price falling within the lending criteria of four-and-a-half times the average income.
The North East ranks second, with 33% of all local authorities remaining theoretically affordable for a single buyer.
It is followed by the North West at 17%, Wales at 14%, Yorkshire and the Humber at 13% and the West Midlands at 3%.
Joint incomes
The research by Alexander Hall demonstrates the importance of a joint income when buying a home.
Taking into account a second average income alters the figures and sees a massive 82% of local authorities across Britain being able to cover the average cost of a home at four-and-a-half times their joint income.
At a regional level, this climbs to 100% of local authorities in the East Midlands, North East, North West, Scotland, Wales, the West Midlands and Yorkshire and the Humber.
While some local authorities still remain out of reach for homebuyers with joint incomes, the majority of areas in the East of England (at 79%), the South West (at 70%) and the South East (at 63%) also sit within the boundaries of affordability.
However, affordability has reached crisis point in London. Even with a joint income, the average homebuyer in the capital can still only afford to purchase in 30% of local authorities based on four-and-a-half times joint income versus the average house price.
Six times income multiples
It comes amid lenders examining new ways to help borrowers with their income multiples.
Earlier this week, Nationwide announced it is offering first-time buyers the ability to borrow six times their income, with a minimum deposit of 5%.
Stephanie Daley, director of partnerships at Alexander Hall, said: “Higher interest rates have somewhat dampened property market performance in recent years and we’re only now seeing house prices start to recover with respect to consistent levels of positive growth.
“Despite this, property values remain close to historic[al] highs and affordability continues to be a key issue for many homebuyers.
“This is down to the fact that earnings growth simply hasn’t been sufficient enough to help bridge the gap and so for many, what they are able to borrow isn’t sufficient enough to cover the value of the home they wish to buy.
“As a result, we’re seeing more lenders continue to think outside the box and drive innovation within the sector in order to assist homebuyers with their aspirations of homeownership.”
She continued: “This includes initiatives such as enhanced affordability, allowing some borrowers to potentially secure up to 5.5 times their income.
“This extra leverage can make all the difference in many locations across the market, or it can help existing homeowners when it comes to creating that extra bedroom or all important outdoor space.”