Yes its one time for android, if you’re earning money with ads or purchases, google will take 1/3 of that amount, then you will have to figure out taxes on your own and there’s also some special policies for selling online goods in India, but if you’re just making apps - its one time fee to be able to upload them to google play store, or you can just distribute with froid/github for free, which is a great route as well
My boss legit says that he will give me some time to work on it every 2-3 months and then drops a “customer requires X feature and I promised that we will deliver in one week”. And mind you we have to patch up to 3 major versions in the past to back port the new feature because client haven’t upgraded and won’t in near future… which means sometimes our major releases are 60-70% same as our minor patches for old versions. Semvering much?