Platform similar to Linkedin

Hello everyone, What I really need is a quotation for a platform like Linkedin, but with restricted acces, where no one can enter freely. It is about what you ask in the sign up page, and we match the data with already existing data, so we know that who is entering the site is not fake. So, what would I exactly need? We are a startup company, and of course I need to start with a beta version to show investors. But here's the list of most of the features the platform should have: - Ability to detect interpersonal relationships (by training courses, past employment, present, studies, etc). - Ability to send invitations - Complete profile: compulsory basic (name, region, specialty), other optional profile (training, education, full career, associations, groups ...) - Full search engine: keywords, region, specialty, industry, etc. - Possibility to link with Twitter: to share from Twitter to the platform (like Linkedin). - To contact members to connect each other - To be able to see who was viewed my own profile - Privacy settings (to be defined) - Possibility to request recommendations - Show, with the contacts I have, who I can reach (degrees of separation) - To receive information of my network when someone makes a change to their profile - Possibility of incorporating a webinar tool - Payment gateway - To be able to use my email address to check if there's people in the network I already have as a contact - Public board to share tests, jobs, research studies, research grants ...: a bulletin board - Something more specific than this: an exclusive section of publications and ability to create open / closed groups to specific members. - Insert job vacancies (job postings) - Possibility to create groups of open interest (mini communities within the community), for example, a group of XXXX in Barcelona, a group of European XXXXXX ... - Ability to upload images / videos / files and share (links with slideshare, youtube, flickr ...?). Sharing content must be easy, and in all formats: word, excel, pdf, powerpoint... - Difference between standard users and premium users. - Possibility of introducing advertising (through banners, skyscrapers, etc). - To be able to create corporate pages for companies. So that's all for now! Thanks in advance, and if you have more questions, please let me know.