If an improvement will be financed by an obligation and the obligation will be secured by the pledge of assessments, the district must enter into an agreement, which may be the development agreement, governing the financing of the improvement before the issuance of the obligation. An obligation issued under this section may be in the form of bonds, notes, or other obligations, payable wholly or partly from assessments, and may be issued, by public or private sale, in the manner provided by Subchapter A, Chapter 372, Local Government Code.