1. A method for selling custom business software enabling a software seller ( 10 ) to offer a custom software application ( 20 ), having a software source code ( 30 ) and at least one software document ( 40 ), for sale to at least one prospective software buyer ( 50 ), wherein the software seller ( 10 ) submits the custom software application ( 20 ) to a software exchange marketplace ( 100 ), having a qualified software application inventory ( 200 ) searchable by the prospective software buyer ( 50 ), the method comprising the steps of: (A) associating a custom software application submission log ( 300 ) with the custom software application ( 20 ); (B) appraising the software source code ( 30 ) and the software documents ( 40 ) for commercial feasibility by: (i) searching the qualified software application inventory ( 200 ) for similar software applications and recording a search result ( 310 ) in the custom software application submission log ( 300 ), (ii) comparing the software source code ( 30 ) with a source code qualification standard ( 400 ), having a program organization component ( 410 ) and a program execution component ( 420 ), wherein (a) comparing the program organization component ( 410 ) with the software source code ( 30 ) identifies at least one software code deficiency ( 330 ), and (b) executing a test script ( 120 ) with the software source code ( 30 ) and comparing an execution result with the program execution component ( 420 ) identifies at least one software execution deficiency ( 340 ), whereby the software execution deficiencies ( 340 ) and the software code deficiencies ( 330 ) are recorded in the custom software application submission log ( 300 ); (iii) comparing the software documents ( 40 ) with a document qualification standard ( 500 ) to identify at least one document deficiency ( 350 ) and recording the document deficiencies ( 350 ) in the software documents ( 40 ) in the custom software application submission log ( 300 ); and (iv) comparing the custom software application submission log ( 300 ) with a final review standard ( 700 ) and determining whether the custom software application ( 20 ) satisfies the final review standard ( 700 ); (C) qualifying the custom software application ( 20 ), when the custom software application submission log ( 300 ) satisfies the final review standard ( 700 ), by creating a qualified software application ( 800 ) having a qualified source code ( 810 ) and at least one qualified software document ( 820 ), wherein (i) the software source code ( 30 ) is transformed into the qualified source code ( 810 ) by correcting at least one of the software code deficiencies ( 330 ) recorded in the custom software application submission log ( 300 ) and by correcting at least one of the software execution deficiencies ( 340 ) recorded in the custom software application submission log ( 300 ), whereby when the software source code ( 30 ) satisfies the source code qualification standard ( 400 ), the software source code ( 30 ) becomes the qualified source code ( 810 ); and (ii) the software documents ( 40 ) are transformed into the qualified software documents ( 820 ) by correcting at least one of the document deficiencies ( 350 ) recorded in the custom software application submission log ( 300 ), whereby when the software documents ( 40 ) satisfy the document qualification standard ( 500 ), the software documents ( 40 ) become the qualified software documents ( 820 ); and (D) listing the qualified software application ( 800 ) in the qualified software application inventory ( 200 ).