Marie Grundy - Managing Director of Residential Mortgages and Second Charges
In fact, it started life in 2004 with a much narrower focus - to allow Harvard University students to connect with one another within a walled garden.
After some initial success, it soon spread to other universities, then workplaces, before opening its doors to anyone aged 13 and over in 2006.
In other words, it had gone mainstream.
In a way, when I think of Facebook, I can't help but see parallels with the evolution of the second charge mortgage market here in the UK.
We'll never see second charge mortgages match Facebook for popularity - 2.8 billion borrowers might be a bit of a stretch - but like the social media network, these loans were once considered a niche proposition.
For years, many people perhaps unfairly, lumped second charges in sub-prime and bad credit.
But I'd argue that today, second charge loans should be considered mainstream products and a mainstay of any broker's armoury.
Data from the Finance & Leasing Association shows that second charge lending soared 40% year-on-year in April.
In the past 12 months, second charge lenders wrote nearly £1.5bn worth of business. This stat alone shows that this is no longer a small, peripheral market.
One of the main drivers of that growth is, of course, the rise of the product transfer (PT), which accounted for more than 8 in 10 residential refinance cases in Q1, according to UK Finance.
The benefit of a product transfer is that the borrower doesn't have to go through an affordability assessment. The drawback is that they are pound-for-pound transactions, meaning the borrower cannot release further capital.
Therefore, those borrowers who have additional borrowing needs must look at a further advance, a personal loan or a second charge. The growth of the second charge market over the past few years suggests they are increasingly choosing the latter.
In our experience, most second charge borrowers are people who have additional borrowing needs and have an attractive first-charge rate that they don't want to disturb.
Importantly, they are not typically the type of borrower you would associate with sub-prime or bad credit - far from it.
Our own data shows over 80% of our borrowers currently have a High Street mortgage and typically qualify for one of our top-tier products.
The vast majority of these are employed, rather than self-employed, and have good to excellent credit scores.
We have also seen a sharp rise in the number of borrowers with high incomes who want to raise additional capital to make high-end home improvements or to invest in another property, such as a holiday let.
That shows there is demand for this type of finance among high-net-worth borrowers, which is why we recently developed an interest-only product aimed at these people.
Once borrowers and brokers take the time to learn a little about second charge loans, the attraction of using them becomes obvious.
The difference between first and second charge rates has narrowed over the years, removing one of the barriers to taking out one of these loans.
Borrowers also find that second charge lending criteria is often far more accommodative than what's on offer int he mainstream mortgage market.
For a start, loan sizes tend to be generous, with borrowers often able to borrow up to £1m with a number of lenders.
Second charge providers are also often more flexible to the needs of self-employed borrowers, who could be eligible for a second charge with a minimum of just 12 months' trading history.
Another attraction is the speed of the second transaction. Second charges are arranged with streamlined legal requirements and often can proceed with an automated valuation. For expert packaged cases, it is not uncommon for cases to reach the offer stage within a matter of days.
Over the years, I have often heard from brokers that they would explore a further advance before entertaining the idea of recommending a second charge.
That's fine. In some cases, a further advance may be the best option for a borrower. But often, criteria are more restrictive, transaction times are slower, and the broker loses control over the process.
Other brokers have told me they don't have any clients on their books for whom a second charge mortgage would be appropriate.
In the past, that may have been the case. But second charge lenders' offerings have come a long way over the past decade, to the point where they have a solution for most UK homeowners.
Like Facebook, the second charge market has gone mainstream.
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