Hiring A UX / UI Designer

Payment: % of Project, Cash/USD/Fiat
I am looking for a pretty decent UX / UI Designer. I will need the designer to take features of an app and design the apps, whether its a saas product or a mobile app. I need to see a portfolio of your work before hired. If interested, please email portfolio before committing.
I am willing to pay $150/screen but I need to see that your capable of the work.