Hello Allen and welcome to The LOC.
I have owned my Mk4 for 6 years now and she has never broken down nor has she ever failed her MOT. The exhaust on Mk 4 are Stainless but are prone to split on a v section which can easily be repaired for around £40.
Mine has done 142,000 and I just get her serviced once a year by my local garage that has serviced the family cars for the last 27 years. I had a number plate bulb go on me and I also replaced the battery which was done by Lexus for about £90 and had a 5 year guarantee with it. that was about 3 years ago now. The one they took out was the original battery she was delivered with. Apart from tyres, I use Falkens I have never had to worry about anything else. Oh yes I had an LPG system fitted when I first bought for for £1400 and its never missed a beat. There is a 85litre tank in the boot where the spare sits and there is still plenty of room.
This car is the best car I have ever owned I still get a kick out of getting into her and starting her up. All the eulogy's about carpet rides, comfort and the fantastic stereos is all true and more.Make sure the Cam belt has been changed as this is quite a costly item to get done. Good luck with your hunting. Mike.