22's 44's
You can pick a timed out robinson up for very little money at the moment. It can be very hard to get rid of one (in the uk) as with the dollar rate as it is it works out better to buy a new one. Remember a factory rebuild machine will be worth less than a brand new one.
As far as I know there is no age that they cannot be rebuilt from.
I have seen 22's for £15k but whether they sold or not is another question.
Are you sure you want a 22?