You can sell it and prices are somewhat market driven but with complicated taxes and limitations to prevent speculation (flipping). It's affordable because, as public housing, there are numerous subsidies, incentives, etc that the government provides to make the initial down payment and subsequent installments as easy as possible.

it still exists, and you avoid it by claiming to be a relative visiting. Just make sure you don't bring large amounts of luggage thru the front lobby, or make a nuisance in the building.

Besides, Singapore is a nation where you probably don't want to break any laws a foreigner. Abetting fraud often is a punishable offence, and you might just become part of a crack-down on illegal subletting to set an example.

That is not an argument for implementing it at home.