from what i know the 494 hymer is the smallest hymer,i never drove one with the 1.9 engine so cant comment on what its like, ours is the 2.5td engine with the 544 layout which is bigger than the 494 but a very common and popular layout . hymers are well put together and if looked after can last well,check for rear fitted seatbelts and any service documentation for both van and habitation, also any mot/cvrt test,
i'm sure more experienced than me will come along with more advice, best of luck and whatever you do dont rush!