During the early stage before you need/can afford a lawyer, use one of the many tools that gives you a good enough template. I've copied a few for me and others from https://commonpaper.com
Can't a creative lawyer almost always find a loophole in any contract? I don't think anyone's going to sue you if you sell a 60€/mo SaaS, esp. if you just hand the customer back their money. Obviously, if you're selling million-dollar medical hardware, your risk profile might be different.