Whereabouts are you, Charlie?
To add to what Twizzel says, if you buy ewes with lambs at foot, you can either sell on the ewes later or send them for slaughter too. That needs more careful planning of course, but for example we'll have ewes who will naturally be lambing for the last time this year and would fit in with that.
If you're not planning to breed from these animals, I wouldn't worry too much about them being rare breed. Instead, concentrate on getting something easy to handle and not prone to escapology (been there, made that mistake).