So train them. Give them a general aptitude test, tell them you're taking a chance and hope they'll stay for at least three years and give them mentors and a couple of months to come up to speed or they'll be let go
Startups are a different story as time to market is crucial and you have almost no slack.
In other industries , new startups seem to usually come from people with experience who have been round the block who have some idea of what is required to ramp up a company in the sector.
In technology it seems that if you haven't founded a company in your 20s then you have "missed the boat".