I am analyzing the effect of gender on homeownership in the US and I keep finding that my female dummy is insignificant after I add age and age squared to the regression. I am using probit model with dependent variable of value 1 for homeowner and 0 for not. I also tried a model with age and female interaction term and then female dummy turned out to be significant. I was trying to see if there is some correlation between female and age but it doesnt look like it. I only notice that there is more older women then men. I am not sure which tests to run to see what is the issue and also if it would be justified to include the interaction term or should i report that the female dummy is not significant?