A consultant who also runs a small product business, or someone with a day job and an active side project, runs into a real design question that a single-role professional never has to think about: does one card even make sense?
If the roles are closely related, one card can work
A "Marketing Consultant & Copywriter" title on one card is coherent because both roles serve overlapping clients and skills — a single card with a slightly broader title covers this well without confusion.
If the roles are genuinely unrelated, separate cards usually communicate better
An accountant who also sells handmade furniture on weekends serves two completely different audiences — a single card trying to cover both risks diluting or confusing whichever context you're actually in at the moment.
Consider context, not just the roles themselves
Handing your "day job" card to someone you met through your side project (or vice versa) can send a slightly off message — carrying two clearly distinct cards lets you match the card to the actual context.
A shared personal card with a QR code can bridge both
For some people, a single simple card with just your name and a QR code linking to a personal page listing all your ventures works better than choosing one identity to lead with — particularly useful if your roles shift over time.
Whatever you choose, keep each card focused
Trying to fit two unrelated businesses' worth of detail onto one card usually produces a cluttered result. If you do go with separate identities, give each one its own clean, focused design rather than compromising both.