Hi there, I can't speak to purchasing young hens, as we have always raised ours from chicks, but we've tried several different breeds (all either eggers or multi-purpose breeds), and by far our favorites so far have been Isa Browns and Speckled Sussex! Our Isa Browns are SO calm and friendly compared to most other breeds we've had (even as chicks), and they are VERY productive layers (we're just on their first winter now, but they have all been laying almost daily since they started in the fall; our previous batch were mixed breeds and definitely laid fewer eggs their first winter, even though they started laying around the same time frame).
The Speckled Sussex will be harder to find, and they're a multi-purpose breed and less productive egg-layers but excellent additions to a mixed flock. They are particularly beautiful, as well as very calm, friendly, and docile. They seem to get along with everyone with very little fuss, and also have had far fewer health problems than some of the others we've tried.
As I mentioned, we raised ours from purchased chicks, and as we handled them a lot from the start, most of ours are relatively friendly and easy-to-handle, with the exception of our Barred Rock rooster and the Lakeshore Eggers. I would definitely stay away from the Lakeshore Eggers - although they lay prolific and gorgeous green eggs, ours had numerous health problems, are very flighty, mean to other chickens lower on the pecking order, and have been generally a pain to deal with. I've also heard some not-so-good things about Rhode Island Reds in this regard. If you like the look of the Rhode Island Reds, I would suggest looking for Buckeyes instead. They look very similar, but seem to have a sweeter temperament and are also great layers. Note that they are also quite heavily feathered, and seem very uncomfortable in hot weather, which is why we no longer keep them.
We've also had Gold-Laced Wyandottes, which are dependable layers and quite beautiful, but again, don't fare too well in our hot Ohio summers.
Our Isa Browns are our newest additions, and so far they've all been very healthy, hardy, and productive - and are so friendly and curious they will all walk right up to you and let you pick them right up - no problem! (I really wanted to have more different breeds in this last batch as well, but that's all
Tractor Supply had when I got them, and so far, we've been extremely happy with them!) If you are getting a mix of different breeds, I would definitely recommend at least 2 of each, and try to get them all at once from the same source so they can grow up together.
Good luck with your new flock!!

Rose.