In most cases - for example translations and graphics - one can build a portfolio just translating or designing a few things, whether their are required/paid for or (rather) not. The one can see if they have talent / they can do it right. Without a portfolio I'd see them as just lazy beginners, hence my answer.
Aside from portfolio, if you learned your skill formally (e.g. in university or bootcamp), you could show the degree/certificate that you have. On some cases it's less valuable than portfolio, but it's better than nothing.