Summarize:

There are a large variety of app-building tools available, ranging from free to quite expensive. Most of the free options have very limited publishing options, or may force you to include ads (which you won't receive revenue for). If you pay for a program, you are more likely to be able to publish the app yourself and monetize it however you'd like. Some of the most popular tools for Android app creation include: ShoutEm Appery Mobile Roadie The App Builder Appy Pie MIT App Inventor AppMakr Most of the popular app-creation programs allow you to take online tours that can give you an overview of how the program will work. This can give you a good idea as to whether or not the app will be good for your needs. When touring the program, ensure that it will be powerful enough to create the app you want. Most app creation programs are collections of prebuilt functions that you can string together to create a cohesive app. Many of the programs listed above have free versions or trial versions available. Use these to get a feel for each piece of software and find the one that suits your needs and skills the best.
Read up on your options. Take a tour of each service. Try a few different programs.