How to afford half a million dollar hdb flat ? 
Actually half a million dollar hdb flat is affordable, mainly
because interest rates in singapore is low. Didn't check but
2%?
Assuming 2.5% to service the loan it is $1042.00 interest
payment per month.
Therefore it is affordable.
Question is how long will it take to own the flat. Also taking
into account 99 year lease. The real question I would be asking is
"is it worth it?"
On the other side also have to take note of what you could do
with it most common example "how much would I get per month if I
rented it out?"
So once all these are considered then its easier to come out and
say "is it worth it?" "not worth it?" "too expensive?" "too
cheap"