I prefer working with companies where I can create value versus in companies where I can't. If your small company thinks their internal one-off AR system is important enough to hire a dev for, that should be worth Serious Money (TM) to the company. If it isn't, tell them "Look, you trust me to deliver wins for the business. This engagement isn't a win for you. If you absolutely need that system worked on, I can recommend someone for it. But let's talk about somewhere where I can make you a couple hundred thousand dollars: ..."

Would you not get paid?

No, of course you get paid. The client bears all execution risk. That's why, when you make them 10 million, they get the vast majority of that 10 million. If clients expect you to shoulder downside risk then they should expect you to capture much of the upside. (Here's words I like: "Well, if you expect me to bear the risk for this project, I want to share equitably in the rewards, too. My sense of equitable is that if I'm responsible for doubling the company's sales I should end up owning half the company. Or, you know, you could just pay my rates.")