Early databases available for the PC market were simple two-dimensional solutions and were essentially designed as a record-keeping system. However, when computing power increased, the advent of the relational database became an affordable option. Applying the rules proposed by Edgar Codd, the Database Management System (DBMS) became a reality, with products such as dBase being widely implemented in the desktop market.
You'll need to include more than a basic level of development and calculation in your spreadsheet. There are lots of free spreadsheets on the web. Most of which are very simple and easy to build. People aren't going to buy a spreadsheet that they can get for free. Take yours to the next level by adding all the value you can imagine. Then research on how you can offer a little bit more on the development and functionality side.
You could make money doing something you love (or like [or maybe not so much but just really good at]). It's great to see a spreadsheet come together, and usually a lot better than what you originally envisioned. Especially when the dang thing works.
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'.
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