A text message is probably is enough to charge someone with a crime depending on the content of the message. A conviction based solely on a text message might seem unlikely, but without knowing the content of the message it's tough to say. There is certainly no requirement that you need to be caught with drugs and a scale.
If you've been charged with selling marijuana, the best thing you can do is contact an experienced local attorney. Your attorney will be able to evaluate the strength of the state's case and may even be able to suppress the evidence found in the text message.
They can charge you, but it's very doubtful they can convict you based on a text message alone. There usually needs to be more evidence to convict, such as marked money, an observed sale, etc. Just talking about selling weed doesn't prove beyond a reasonable doubt that you sold weed. If you are charged with selling marijuana, feel free to call me for a free consultation. These are the kinds of cases that I love to fight. David Pullman 866-244-5004