Your business card is considered an advertisement and must follow the same TREC and NAR rules as all other ads.

Fact. An ad is considered any form of communication by or on behalf of a license holder designed to attract the public to use real estate brokerage services. This includes publications, brochures, radio or television broadcasts, business stationery, business cards, displays, signs, billboards, and all electronic media—email, text messages, social media, and websites.

The only exception to the advertising rules is communication between a license holder and that license holder’s current client.