Here is a list of fee / taxes you will need to consider when buying a condo
purchase stamp duty
* mortgage stamp duty
* legal fees
Of all the fees / taxes, it's the first that's most painful. Here's how you calculate it:
* for the first 180,000 of the purchase price: you pay 1%
* for the second 180,000: you pay 2%
* for the remaining: you pay 3%
Since, as an expat, won't be buying a HDB flat, you can safely assume the price of your condo is more than 360,000 SGD. So it's 5,400 + (purchase price - 360K) * 0.03.
For example, if the purchase price is 1M:
* 5,400 + 640,000 * 0.03 = 24,600
The stamp duty on mortgage is about 500 SGD and the legal fees can go up to 4,000...
I hope that helps.