(a) When a special assessment district is created, there may be included in the assessments (1) all of the cost of acquiring, installing, making, or constructing the local improvement;
(2) the costs of all engineering and surveying to be done in connection with creating the district or improvement;
(3) the cost of mailing and publishing notices;
(4) interest on interim financing;
(5) the cost of legal services and other expenses incurred in the formation of the special assessment district;
(6) the cost of completing the improvement and financing the improvement, including the issuance of bonds.
(b) The total amount of the assessment roll may not exceed actual costs, but actual costs may include reasonable estimates of the costs to be incurred in connection with issuance of bonds.