Is it safe to buy preloved breast pump? If yes which brand and model would you recommend (double pump preferred) for going back to work?

I wouldn't be able to say that its safe or unsafe, but i would think that it depends very much on your c9mfort level. Some would say its not safe, wheras others would say otherwise. I personally have a preloved pump, i never had any issues. You can try Unimom, Carousell is a good option. Hope this helps.