[piyushdinde]

Yes, you are right.

There is no fixed model to this but largely what you said is what the standard is!

Some upfront cost is always taken from the customer before starting the project and then paid in full once project is delivered.

Post that it depends what customer wants. They can keep paying you to maintain it regularly and fix bugs. Also you can charge them for some additional feature development. (This is called account expansion revenue in business terms.)