These are the pros and cons of selling spreadsheets. The real beauty in this idea is that you could do the work once and there is no limit to how much you can earn, especially with effective use of the internet and other mass communication tools.
At present, some of the most requested types of spreadsheet packages in the market are: 'Spreadsheets for Small Businesses' and a subset of that: 'Spreadsheets for Actors'.
You may want to create a workbook with multiple sheets for various aspects of your budget. You can have one sheet that keeps track of savings and investments and another sheet that lists your monthly bills.
If you have Microsoft Excel, you can create budgeting spreadsheets to help you manage your money. Instead of buying expensive software that will only be used for your budget, spreadsheets can be used for a variety of tasks. If you don't have Excel, you can find free spreadsheet applications online in which to manage your budget.