How much do I charge to set up a CEM app for a small business??

I've been asked to set up a CRM for a business owner. This is for a small business in the service industry with 100 or so clients what will needed to be integrated into the app. I am at a loss with how much I should be charging this person, and if it would be better to give an hourly or flat rate? I'm not sure yet if this will be a one time set up, or ongoing CRM management but for now just set up. I've done social media management and similar things in the past… Should my rate be in a similar ball park?