Like PIT said, it all depends.

Just because something doesn't work for one person, doesn't mean it won't work for you. I had picked up a 2 year old female that was 1000g that came with a similar story. I got her settled and fed her a small rat after a week and she fed no problem. Week after week she took small rats and after 5 feedings I put her on Mediums and the rest is history.

Sometimes it is not the snake, it is the husbandry or feeding process. This is not always the case, but with any new snake it is best to figure out what feeding process works best for them.