Noth­ing in this Code shall require changes in the plans, con­struc­tion, or des­ig­nat­ed use of a build­ing or struc­ture or por­tion there­of for which a law­ful per­mit has been issued or which has been actu­al­ly begun with­in nine­ty (90) days after this Code becomes effec­tive and which entire build­ing or struc­ture shall be com­plet­ed, as autho­rized, with­in two (2) years there­after.