Course classing while making Application scorecard

Question

I have a set of data for which i am developing an Application score card

In this data, the applicant's income is only rank ordering if i break it into salaried and self employed. But if i do so, and when creating dummy variables, i get zeros / nulls for all self employed customers in the salaried income column and vice versa

Example

Income sal         income self emp

50000                  NULL

NULL                    300000

NULL                    568900

54333                   NULL

the above is just to show my issue