They should borrow short-term money to buy tools or get meaningful educations/licenses, and then pay off the debt, fast. This way, they will build a credit history. That’s the wisest strategy. But if there is a temptation to go into consumer debt, then it’s best not to borrow at all. Like other addictions, the first snort should be avoided.
Borrowing is not an evil. It depends of what you are borrowing for. If your debt supplies tools, education, or a comfortable but modest place to live, then it’s a tool of dominion. But if debt is used to buy depreciating assets, it is a curse. Most assets depreciate. Buy them used for cash from someone who is strapped for cash.