I would be cautious with the legal aspect. In Texas I don’t think you can use text messages as a a legal document. I had clients that only wanted $1500 of work, and I like to think they were impressed with my work and gave me additional jobs. $15,000 later they wanted to argue on the price. I updated the bid every time they requested an additional service, however a lot of it was verbal or text. If you do use text I would strongly recommend that you would follow up with an email summary. Every Friday I would send an email with a running bill. It got me out of a potential legal issue. My 2 pesos worth.