Is it permissible, in Sharia, to take a percentage ranging from 1% to 3% of the collateral's value in exchange for appraising its value and type for the customer?

If the mortgaging process is Islamically permissible, then your work in evaluating the mortgage and taking a known fee (1% or 2% or 3% of the mortgage value) is permissible. However, this permissibility is conditioned on the evaluation of the mortgage not being part of your primary job for which you receive a salary; if you are a salaried employee for mortgage evaluation, then it is not permissible for you to take any additional fee from the customer.