What are the properties that Foreigner can buy in Singapore?

Property in Singapore is generally categorized as HDB, Private Condominium and Landed property.
Foreigners can purchase private condominium, regardless whether they have valid long term visa in Singapore.  

What is the cost involved for property purchase in Singapore for foreigners?

Generally speaking, Singapore property price is quite transparent and the purchase process is standardized and well regulated. All the cost are listed below:
1.    Cost of the property = purchase price
2.    Buyer stamp duty (3%~4% of the purchase price)
3.    Additional buyer stamp duty (ABSD), 20% of the purchase price
4.    Legal fee $2500~$4000

What is the ongoing maintenance cost of property in Singapore?

1.    condominium management fee, usually it is in the range of $300 ~$800 for three bedrooms.
2.    Annual Property tax, usually is around $100 for three bedrooms type for own stay
 

What is the payment schedule?

There are two types of payment schedule.

If you purchase BUC (built under construction, 楼花), there are 10 phases of payment according to construction progresses.
Take example of private condominium SGD$2million.

If you purchase resale units,
1.    Booking 1%
2.    Exercise option, usually 2~3 weeks, 4%
3.    Tax, usually 14 days.
4.    Completion, usually 10~12 weeks, 95%

What is the difference between foreigners and local in regards to property purchase?

The only difference is during purchase, foreigner need to pay ABSD (additional buyer stamp duty) 20%, while citizen ABSD rate is 12% and 15% for second and third property respectively.

Other than that, there is no differences in terms of renting out property or selling properties.  

Is there any property gain tax in Singapore?

Singapore does not tax property capital gain.

Can I sell my condo to foreigners and locals?

Yes, there is no restriction on this. You may sell your private property (condomium) to both locals and foreigners.