There is a good point in the post that no one seems to mention. Negotiate on the scope. Please, for your own good, do that. It sucks so badly when you a finish

There is a good point in the post that no one seems to mention. Negotiate on the scope. Please, for your own good, do that. It sucks so badly when you a finish a project for a nice amount of money, the client says 'oh I have this project... can you take a look? I just need a quick fix', and you believe that a quick fix is a quick fix but in reality, it's piece of crap that you are not sure how does it even work. Why it sucks? Because I feel bad to tell the client to go away after he spent $XXXX on me. And I wish I knew about the retainer contracts when I started... Random hours for maintenance for old projects sometimes can kill you.