Probably the cheapest 120 film cam you could get here is the Seagull (Twin-lens reflex cameras).
I don't knoe of which place has it, but K-13 Marketing has a few nice models on their shelves (2nd floor, Peninsula Plaza).
Seng Chong is the distributor.
Prices are around SGD $300 give or take.
Alternatively, if you have a little more moolah and may want to expand later, get a 2nd hand 6 x 4.5 or 6x6 SLR. Whether you want a metering prism finder, or a basic pop-up with maginfyer finder is up to you.
A basic set-up with a standard lens and 1 magazine should cost you between $800 - $1300.
Reliable brands should be Mamiya and Bronica.
Do note that Bronica is dying though.
However, lenses and accessories are widely available in the 2nd hand market.
Blads are out unless you have a larger budget.
A few labs cater to 120 developing and printing are available as the 120 format is still the mainstay of many professional photographers, but it would only be a matter of time before relativelt affordable digital backs are made available to the masses.
You could post this in the 'Medium Format' Section where I'm sure many more experts could assist you.