[nivertech]

You can sell support and warranty contracts.

Usually it will be for software you helped to develop originally, or the one you know well (commercial or open-source).

I do this when customer asking for long-term support. Some companies are moving slowly, so it will take time to them to discover bugs.

You just adding XX% to the contract, the added benefit that you will have an incentive to reduce the amount of bugs/defects in your code.

Several times it was like free money, other times it was several days of work fixing bugs. I think worst case it was a week of work.