Great advice here. I can tell you're in the "beginging to think about it" stage, and the fact that you are asking about the pro's and con's of breeding tells me you are responsible. This is a sensitive topic here because the ones who breed know how many things can go wrong, and your bitch could have a difficult time. You even have a risk of loosing her (not sure what the % is) as well as the pups. Breeding small dogs, I take from reading here in YT, does come with higher health risks than other larger breeds.
There is also the issue of adding to the dog "pup"ulation (clever eh? he he) when the shelters are full of unwanted dogs. The puppy mills are a terrible business and dog lovers are very upset about people making money off of breeding dogs. The dogs are usually kept in deplorable conditions and this is very upsetting to us. This is a very big problem, and people who love dogs can get very emotional about breeding. So, you will hear these opinions about people breeding for money. Some here are so upset about it (deservingly) that they have been too harsh with people such as you, who ask about breeding.
I have to say that so far, the replies have been great. I'm proud of YT with this thread. It is my opinion that helping people such as you decide whether to breed or not, by providing good information, or guidance is a more positive route than getting mad about your inquiry, especially since you are just "thinking" about it
Good luck with your research and thought process.