Tier 1 (General Dependants)

[khan10200]

I came in to the UK as student in August 2005. Later in September 2007 I got HSMP. In September 2005, my HSMP visa expired and I switched to Tier 1 (General). Now I am planning to apply for my dependants. They include a wife and four children of which one child is older than 18 years so he is not a legible ‘dependant’. So I have to now apply for my wife and three children under 18. I need following information if anyone can help I will be obliged:
1. I am renting a 4 bed house privately. The tenancy agreement is signed between me and my landlord and does not include any witness/attestation etc. Is this sufficient or it must be certified/attested/witnessed by someone and who can certify this. Moreover what is minimum required tenancy term? One year or more
2. Where can I get a certificate for the adequacy of the accommodation. A solicitor, a property agent or any other authority. (The certificate saying that the accommodation is ‘suitable’ for this size of family.
3. Do I need to produce a certificate regarding never having recourse to public funds. Which authority issues this and what’s the procedure.
4. The policy guidance states that any children over 16 years must demonstrate that they have not started independent life. I am confused what kind of evidence can be produced to demonstrate this.
5. The UK visa web site states that the fee payable by each dependant is equivalent to what I had paid when entering the UK. I entered as student, then switched to HSMP and then to Tier 1 General. I am confused which fee is applicable.
6. Any other requirements please.