2 Things:<p>I always charge 25% up front (in case they cancel halfway through, or just take forever to get started).<p>Once the project is done, maintenance is always hourly with a 1 hour minimum. Even if it only takes 5-10 minutes, the bill will be for an hour. As long as you are upfront about this, it will give them incentive to batch the changes into groups, and also make it so you're not taking 5 minutes out of every day to do some minor change.<p>There are the hidden costs that clients don't consider: Stress and time to plan to do the change, firing up the environment while stopping what you're working on, changing, testing, uploading, emailing the client to let them know it's done, doing an invoice, following up with payment, cashing the check, etc. 5 minutes of work generally takes an hour of your time overall.