Webagency Looking for a Mobile Freelances for a 3 months Job

We are a France webagency part of a big advertising group We are looking for a freelance developer that we can entrust developing each month for mobile app projectss. We offer a fixed monthly salary to be paid at the end of the month and all-inclusive of all required activities. It is therefore a fixed salary for the development of at least 3 / 5 projects per month for a minimum of 3 month of contract. The freelancer we are looking for should be aware that we are looking for both Apple Iphone/Ipad environments and Android (preferred) and have graphics capability for create complete apps from development to that of mock-up logos etc.. The salary is $ 500 monthly (payment avery 30 days with Paypal) Specifically that we are not looking for other web agency but individual freelancer that can support us in developing our plans and pay a fixed monthly price handling full app development, from graphic to coding. We require also in advance to check freelancer skills with a 15 days test project before sign the contract. Please answer us only if you are really intrested.