Tenancy agreement is not mandatory, a letter from landlord will suffice saying that he is happy to let your dependent stay as long as needed.
The cost of NHS surcharge can be 600 pounds for 3 year visa, and application fee will be around 500 pounds for 3 year visa.

Payslip is not mandatory, you can give a copy of the employer offer letter instead along with maintenance letter.

What is this scheme' name? Or please provide any link for the same.