SINGAPORE - Firefighter Nizar Marican sometimes returns from an overnight shift to find his house cleaned, fridge stocked, and freshly-cooked food in the kitchen - kind acts done by backpackers who are staying in his Tampines home for free.

The bachelor, 38, is a host on Couchsurfing, an international network where locals in each country offer a bed, couch, mattress or sleeping bag to travellers. It is part of the sharing economy, where kindness is the currency.