"저의 집을 사세요!"
Translation:Buy my house!
우리 can only mean 'my' when referring to one's own family members or house; in all other cases, it is the plural of 나, so 'we, us, our'. It doesn't necessarily exclude the listener... I don't know where you got that information. Saying "our house" to your children or spouse who live there would still be [우리 집].