1) Short answer, no, we don't know any reliable second-hand espresso machine sellers.Another opinion (coffee journalist):
2) Coffeeinmalaysia.com is the distributor for Vibiemme machines here. They take care of maintenance for those machines, if you buy one.
3) Vibiemme's the runner-up brand for home machines. The most preferred brand is Expobar (AU based).
4) "Commercial" vs "prosumer" vs "home" are more like promotional terms. You should consider some functional innards - like looking for EFI instead of carburetors in cars:4.1) "Separate boilers" for steam wand and espresso group head - essential if you want to be use both at the same time. Most likely that you will, if a lot of people want lattes at the same time.5) A good grinder is essential also, otherwise the extraction is less controllable. Fiorenzato F4 E nano is highly recommended. It is available from Coffex in Malaysia.
4.2) "E61 traditional lever group head" - guarantees that your group head does a "preinfusion" - meaning that it wets the puck of grounds, before ramping up to full 9-bar pressure - this make the extraction more consistent/controllable.
4.3) For example, these machines take care of both concerns in 4.1. and 4.2.
Vibiemme (VBM) Domobar Super Double Boiler
Expobar Office Barista Minore III
4.4) This site is a reliable source - in this article, they have a brief review of some home-sized machines and a comparison of price and value.
Nuovo Simonelli 'Oscar' espresso machine and Mazzer 'Mini' grinder might be a good entry point. Though he says you could go even lower and try an rm500 espresso machine if you have zero background in pulling shots.
He also recommended the Fiorenzato as above, and the Nuova Simonelli MCI Grinder for comparison.