I would have thought a van would be more suitable for a builder, and VW do some excellent, and reliable vehicles. On the smaller side is the VW Caddy, or the VW Transporter on the larger "Transit" size, both excellent for the building trade.

But, if you want a vehicle which could be dual purpouse, then any of the VW estates are reliable, The Golf or Passat are your choices. Both are very reliable, if maintained well, and can be found at reasonable prices in Auto Trader.

As for any common faults, I don't sell many parts at work for these that could be classed as common faults, apart from Wishbone bushes, and suspension mounts, both relatively cheap to replace.

What you need to do is look around, VAG cars hold there value well, so any used, well maintained car will cost a little more than most others.

Hope this helps a bit.

Stuart