The variable I am interested in is "time living in the area". This only applies to people who were born elsewhere and then migrated to the area in question.
My intuition tells me I would model "migrant" as one variable and "time living in the area" as another, then only place the interaction term into the regression. That way, "natives" would be the reference level and the resulting coefficient would describe the change in my dependent variable with years of residence in case the individual is a migrant.
Is this approach correct, are there any others I should be aware of?