Hey all! I'm wondering what to charge a freelance client on an hourly/retainer basis. I've been working with a client on a freelance basis for the last 6 months on a one-off project. I'm a UX/UI designer helping them redesign one single user flow (about 10 screens total). Now that the project is wrapping up, the client is looking to redesign their entire app and wants to continue working with me on a long-term basis. The project I'm finishing is one very small user flow, but the app ha several features and has never been professionally designed or thought through (it's a big under taking ~ hundreds of hours needed). 

They said they'd only expect about 10-15 hours a month, which isn't moving very fast considering how big the app is. I'm not exactly sure how to move forward on terms of pay and wondered what y'all thought. Here are a few details that may be important: 

- I have 3 years of UX experience

- I have 10 years of design experience (branding and web design) 

- I have a masters in Human-Centered Design and Engineering 

- I work full-time as a UX designer for a University (provides a lot of flexibility)

- the client is in the healthcare industry and a start up (around 15 full time employees, and a handful of contractors) 

- I'll be the only designer on the team 

Thanks in advance for your insight!