Advertisement website

I need to create a website where people will advertise their goods, and where buyers can read the adverts. The buyers will only be able to access the contact details of the sellers if they buy virtual credits (?1 for 3 credits, or 3 euros or $3. 1 credit= 1 contact detail). The contact details of the sellers will be encrypted and only accessible if they buy credits but the rest of the message will be readable. Users from the UK, the USA, Ireland, Canada, Australia and New Zealand will be able to advertise their goods. Flags in the home page will allow these users to access their country page. The website users will be able to advertise using different drop down menus (type of object for sale,main cities for EVERY COUNTRY). The payment page will have to accept UK pound sterling, american dollars and Euros. Thanks.