Depending on how simple or complex you want to be able to account for your income, you may need as few a 2 or 3 income accounts, or as many as 100 or more.
You create income accounts by clicking on the "New Rec" button while viewing the Income Accounts form. That presents you with an empty income record form. You then enter the title of the account you want to create, and specify (by selecting from the combo boxes) what linkages you want set up, as follows:
Income accounts do two things - they account for why the money was given and what fund it is to go into. For example, Pledge "Payments" would normally go for General Operating purposes (to pay for salaries, utilities, maintenance, etc.) and would normally be put into the General Operating Fund. For this reason, an Income Account has combination boxes to specify the type of use the account is to for, and the fund it is to be housed in.
In addition, if you want to have reports group income account by some other schema, you can specify "user defined groupings" by creating your own groupings, via the "Utility Tables" switchboard. Once you have created your own groupings, you may select them on this form in the "Report Grouping Categories" combo box.
Finally, in very rare instances, you may tie an income account to a liability. The effect of this would be to generate a mortgage liability. Normally, you would be better off to simply open the mortgage liability by creating a New record and just putting the opening balance in that field.
From the income account record, you can also link to the Budget for that account, request a viewing of all the transactions for the account for the year, or request a listing of all the income accounts.