When running a 41 year analysis, say from 65 to 105, yet you want a paydown for only 20 years, se the illustration period to 20, click the paydown button, then click it again (turns it off) then change your illustration period to 40 so you can see the 20 year paydown.  Then, in the Other Net Income section you could add Reverse Mortgage Income or Dividend Income from age 86 to 105. 

Definition of “Additional Income” is “net after taxes but before qualified plan deduction”.  For example, if someone is earning $150,000 they have $30,000 of mortgage interest deductions and $10,000 of charitable deductions, then Additional Income is $110,000 for the Qualified Plan Calculator and if they are putting $15,000 into their QP, then Additional Income is $95,000 for Accumulation and Distribution Calculator