If you are doing this as a contractor, then this is partly the client being dumb and you not selling. You tell the client how many hours you can work and part

If you are doing this as a contractor, then this is partly the client being dumb and you not selling. You tell the client how many hours you can work and part time / full time is largely irrelevant. If pressed, tell the client that 20 hours per week IS full time (you have a business to run!) There may be exceptions if the project has stiff hourly requirement needs that you need to fulfill because of a tight deadline, but those expectations should have been set up front (on both sides.) Another exception may be a salaried W2 worker. Even in that case you may only get 20 - 30 good hours of coding in a week, but I suppose everyone has to play the paperwork game.