Over extending their finances on a property upgrade for the sake of 'investment'.
You're exchanging guaranteed and growing retirement funds (OA) and taking on a liability (mortgage) for an investment that is not guaranteed, high quantum (sometimes 20X your income), not flexible, comes with additional fees, and strict laws, which you will die die have to service for 20 to 30 years if you want to keep the house, while exposing yourself to a fluctuating interest rate.
My advice is that your residence is not an investment. Stay in a modest home. Don't stay in a place that costs more than 7X the annual household income.
A lot of the time when it comes to property purchase, people would also buy a house bigger than their budget because they'll say they'll "figure it out" on how to afford it.
And that's just really bad.
I see people having high expenses in shopping, food, travel and even transport.
These are foreseeable expenses which if you can control well, should be able to have a higher disposable income for investment etc. Of course, you should enjoy but not too much.
Another is overleverage to property “just because you cannot see your CPF money.” Unless the property capital gain is 8% a year, or you are getting rent from it to pay mortgage (which is still risky), try to keep it within expenses.
Insurance is also a big thing because many just spend to buy whole life policy without doing comparison with BTIR, adding too many riders to the whole life policy, and generally not in control Nor have a good copy of the coverage they have.