Do not do it for free! You will end up losing lots of money, go broke and get burned out. Either factor it into the quote or say in the quote that it does not include any major revisions.
I factor in tweaks to the design, that will always happen. I do not factor in a completely new design (whether it's graphic design or database design) because what if they go with the initial one? Then they'll want money back since they didn't do a redesign.
I prefer to say this in the quote:
My advertised rate is $xx per hour. For projects of more than x hours, I lower the rate to $xx.
List what you are going to do. Estimate that it will take, say, 25 hours, at the lower package rate.
If any part of the project spins out of control, and it likely will, they need to pay the hourly rate after 25 hours has been spent.
Keep track of why/what/when caused you to go over your estimated time.
Always over-estimate the time! It WILL take longer than you think.
If client decides to cut out some of the items on the project list, they will want money back. That's why I say that projects of more than x hours get the discounted rate. If they cut out half the project, you are losing money because smaller projects are more costly to execute -- the time you spend with administrative tasks.
Years ago I bought a web development contract from ContractEdge for about $19. It was worth many times what I paid. Your clients take you more seriously when you show them a professional contract like this.