If you want to try to break even, much less make a profit, I would suggest that any rare breeds you get into be something where quality can be assessed *young*... which unfortunately kind of leaves any of the longtails out. YOu don't want to have to raise up lots of chicks for like a year, year and a half, before having a good idea of which ones are good and which not so good. Drastically increases expenses. Nothing wrong with slow-maturing breeds as a HOBBY, but they are certianly not the best projects financially, compared to breeds that can be sorted as to keep/sell-expensively/sell-cheaply at a young age.
(edited to add: there is money in MY chickens, I should know, I put it there myself LOL)
Good luck, have fun,
Pat