If you are getting two baby ratties, (1-3 months old), then I would recommend that you start with a 10 gallon aquarium. This is because most cages large enough for adult rats are not equipt to handle small ratties, and they could escape! If you want to get an open-air cage with bars instead, look into cages meant for hamsters - but don't get the kind with the plastic tubes for them to run through! Ratties get too big and can get stuck in these 'toys.' I currently have two rats in a 10 gallon aquarium, as they are too small for my other cage. For now, it is suitable for them as long as I clean it 1 to 2 times per week. I keep a 'mesh' aquarium-topper on top of the aquarium to be sure they won't escape. You can find this at any good pet store.
As for bedding, I use carefresh, or carefresh ultra. It's the only bedding that I trust as many beddings have addatives or chemicals or ink that is no good for a rat's health. It's soft enough and smells decent, even when soiled. It is kind of expensive though -- compared to the dangerous other bedding. It runs about 6 dollars for a small bag, and 20 dollars for a lage economy bag. The 20 dollar bag is, of course, a better deal.
Buying from a breeder is a smart idea, they seem to care more about the rats than a regular pet store. However, I believe that health problems really depend greatly on the rat. There is no doubt that you have a better chance for a healthy rat with a breeder, but some rats are just sickly with lowered immune systems for whatever reason. All rats are succeptible (sp?) to upper respiratory infections, it just depends if their immune system can fight it off in time. For example, I have one rattie who had an infected finger due to injury which I believe lowered her immune system and caused her to be succeptible to the respiratory infection. We have her on antibiotics now and it seems to be helping (fingers crossed).
I have never heard of the Harley breed, but would be interested to see one. I have two dumbo ratties that are just the cutest.
Good luck! And again, don't hesitate to ask if you have any more questions. I love to talk ratties!