In previous chapter, we have established investment models with debt repayment at the end of the project, well proven in the analysis of real investment projects. In practice, however, a scheme of uniform debt repayment during the duration of the project is more extended. In this chapter, we describe new investment models with uniform debt repayment during the duration of the investment project, quite adequately describing real investment projects. Within these models it is possible, in particular, to analyze the dependence of effectiveness of investment projects on debt financing and taxation. We will work on the modern theory of capital cost and capital structure developed by Brusov–Filatova–Orekhova (Filatova et al. 2008) as well as on perpetuity limit (Мodigliani and Мiller 1958, 1963, 1966). In this chapter we consider the application of the investment models with uniform debt repayment to rating methodology.