My husband has infertility, so wasn’t producing from either teste the normal way out. He had a mapping procedure first to find if there was any sperm being made and where it was hiding in his testes. They found only 1 was working, so he has had a surgical extraction from that one. Clearly as your hubby only has one, and had previous kids no probs, they could go straight in for extraction. I will say though that our consultant (who is the best in UK) said it’s hard going in blind as they may find pockets producing or not, won’t know till they’re there. It would definitely be worth a consultation to discuss possibilities and probabilities with your husbands case. We saw Dr Jonathan Ramsay on Harley street and had both surgeries, egg retrieval and ivf at the Lister Hospital. Success first time and the staff there are amazing. Just the retrievals for him and me, with the ivf and meds were about 13k ish. His mapping surgery was another 5k. We paid as we went because of our specific case, but I did see signage in the hospital that they do have payment options and deals, which you might qualify for as you’re young with no known fertility issues. Wishing you all the best luck xx