I went back to work when #2 was 9 weeks old and was in the office 3 days a week until he was 6 or 7 months, then full-time. I got the Medela Pump in Style (double electric) and it was bought in the US by my friend, for close to $200, and is worth every penny. I agree that you need a good quality electric and Medela is considered top of the line. It is not hands free but it is possible to rig it up so it is, which is what I have done. Everyone varies, but I generally have got about 5 oz. total, sometimes more, sometimes less, which is around 1 feeding for my baby, every session in 10-12 minutes. It is very comfortable and in a nice portable and business-like looking bag.
If I work and pump again, I'd spend even more for the Medela Freestyle which is a hands-free digital and gets rave reviews, but I don't think you NEED it - the Pump in Style will meet your needs.
It goes without saying not to get a used pump. I know some people buy new tubes, flanges etc. and use someone else's but it is not recommended. The money spent on a good pump will still be less than formula for a year and will make it possible for you to keep nursing.
With #1, I was able to hand express A LOT of milk so this may be an option, but I don't think it's practical when you are working away from the home as it could be messy and took longer than pumping does.
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