Are there any Android browsers that support loading a Java Applet in-browser?
Similar questions have been asked here before, the short version, JAVA applets are not supported on Android. The version of JAVA used on Android is not just your run of the mill JAVA so you would need to get a JAVA compiler on the phone first to run any applets. Which I don't think is possible or at least feasible.

Why not just download the Android SDK and make your own app? You don't have to sell it in the marketplace, but if your app could be used by others you could do that which might help recover some money spent on development.