The reason you're valuable as a freelancer is because you know things that their existing developers do not. Take this lack of knowledge as a gift: it's how you can add value to their organization and justify raising your rates. (You do want to select for companies that are open to implementing these dev practices, and sell them on the benefits up-front. But a company that wants to implement all of these but doesn't currently have the headcount for it is a gold mine. It's an opportunity for you to improve the efficiency of a whole team instead of just writing some code.)
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The reason you're valuable as a freelancer is because you know things that their existing developers do not. Take this lack of knowledge as a gift: it's how you can add value to their organization and justify raising your rates. (You do want to select for companies that are open to implementing these dev practices, and sell them on the benefits up-front. But a company that wants to implement all of these but doesn't currently have the headcount for it is a gold mine. It's an opportunity for you to improve the efficiency of a whole team instead of just writing some code.)