You can build a reputation as an expert spreadsheet developer. This certainly doesn't hurt the resume. Using Excelville.com to sell spreadsheets allows you to set up a profile with your work, biography, and other info that certainly makes for good conversation material during interviews.
Rather than having to go through the pain and suffering of learning a new technology and having to experience trial and error development, the best route would be to acquire the services of a consultant, who can identify your needs and create a customised solution. Obviously, the cost of such a project would depend on the size and complexity of the spreadsheet and your requirements. However, you might be surprised at how cost-effective this project would be.
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.
Spreadsheet applications are useful for home and small businesses. Some people keep a home inventory list on a spreadsheet and others use spreadsheets for a variety of applications. Creating your budget and maintaining it is easy when you use budgeting spreadsheets. These are also easy to print out if you desire.