When former disc jockey Gurmit Singh, 59, was diagnosed with a spinal disorder in 2003, doctors advised him to stop working.
But the sudden halt in income made paying the monthly mortgage for his three-room flat in Serangoon a struggle.
In 2009, after racking up a mortgage debt of $18,000, he was forced to sell his flat back to the Housing Board. He then moved into a two-room rental flat in Toa Payoh with his wife and two daughters.
Like him, almost six in 10 public rental flat applicants today are former home owners who had sold their flats.
This is up from 52 per cent five years ago, said Minister of State for National Development Maliki Osman earlier this month, describing it as a "worrisome trend".
Cases like Mr Gurmit's, where unforeseen circumstances such as illness or retrenchment lead to mortgage trouble, are not uncommon, MPs, social workers and tenants told The Straits Times.
They also listed debt, divorce, family conflict and imprudent spending as other reasons.
SOME home owners sell their flats to pay off debts incurred from failed businesses or gambling. And there is usually not enough money left to buy even a smaller unit.
"For many of them, selling their flat is the only way to settle the debt," said Mountbatten MP Lim Biow Chuan.
Part-time dishwasher Ng Mui Keng, 62, used to live in a four-room flat in Joo Seng with her four sons for 10 years.
But when one son owed moneylenders a huge sum, the concerned mother decided to sell the flat and withdraw another $6,000 from her Central Provident Fund savings to help him.
Together with two of her sons and two granddaughters, they rented a place in Mountbatten on the open market for 11/2 years, and eventually moved into a two-room Toa Payoh rental flat in January.
"It's a headache, we had no choice," said Madam Ng, in Mandarin.
"We are just taking it day by day now."
Divorced couples often sell their flats to split their matrimonial assets, and there is a debarment period of three years before they can buy another subsidised flat.
But the proceeds are sometimes not enough for divorcees, especially those with children or low-paying jobs, to buy another unit, said Mrs Lilian Seah, 38, principal social worker with Fei Yue Family Service Centre.
Even if divorcees keep the flat, they often have to sell it off later.
"Very often, the wife is not working or earning a lower wage, and she can't afford the mortgage alone," said Chua Chu Kang GRC MP Zaqy Mohamad.
Senior social worker with Heyday Success Coaching, Mr Alvin Chen, 33, came across a father in his 40s who sold his flat after a divorce, and had custody of his seven school-going children.
"It was a large family with a low per capita income," said Mr Chen, adding that the sale proceeds were insufficient to buy another unit.
"A rental flat was the most cost-effective way in the short run."
Some elderly couples sell their flats to move in with their children, or sell their flats to their children, only to fall out with them later, said Pasir Ris-Punggol GRC MP Zainal Sapari.
Added Mr Lim, who has also seen a few of such cases: "When things turn sour, they're stuck without a flat."
Madam Fion Phua, 45, founder of volunteer group Keeping Hope Alive, met a woman in her 80s who lives in a one-room rental flat in Toa Payoh.
She was kicked out from her three-room flat in Yishun, after her son and daughter-in-law insisted on selling the unit which her late husband had left them.
"She said her daughter-in-law doesn't like her. Her son doesn't visit her any more," said Madam Phua. "At her age, she cannot borrow money to buy another flat."
There are also home owners who get carried away with the proceeds after selling their flats.
"Many have not seen so much money before, they think it's a bottomless pit," said Mr Zainal.
Dr Lily Neo, MP for Tanjong Pagar GRC, cited a family who sold their three-room flat last year and received about $60,000 in cash proceeds.
But the couple and their two daughters exhausted the money in less than a year and had to apply for a rental flat.
"They spent about $10,000 for their daughter's orthodontic and plastic surgery," said Dr Neo.
Mr Zaqy mentioned a family who went on vacations and stayed in hotels in Singapore after getting more than $100,000 from selling their flat.
"By the time they came to me (three years ago), they were living in a van," he recalled.
Madam Norwati Taip, 46, sold her four-room Whampoa flat in 2010 to downgrade to a new three-room flat.
But while waiting for her keys, she spent most of the $126,000 in sale proceeds, paying overdue phone bills, medical bills and renting a car and condominium in Malaysia for two years.
Such spending meant she could not afford the resale levy for her new flat. Instead, she had to move into a two-room rental flat in Jalan Bukit Merah, where she lives with her husband, three children and three cats.
"Nobody told me about the levy, or I would've put aside some money," said Madam Norwati, who is unemployed because of a medical condition.
"I never expected to be living in a rental flat today."