Depends. Standard rule is that everbearing strawberries should be harvested from the get go and June bearing should be harvested after the first year. I personally harvest some the first year, but that is because I haven't seen that the plants are all that much healthier if I follow standard guidance to allow root development. I don't know if that is because my soil is so bad that they get what they get and that is all anyway or if they love the soil so much that they happily colonize it even while bearing fruit. We have a nice long growing season, so I'm sure that helps. The berries taste great and I'll keep doing it this way =)
Now blueberries I definitely don't harvest the first year they try to bear, but they cost a lot more per plant than strawberries and I know they like our acid soil enough to really establish given the chance.
