What you do with the property depends on your financial status and goals. If you are in need of the funds, you should seriously consider listing your apartment for sale. However, if the rental income is higher than your monthly expenses (positive cash flow or passive income) and you are not in need of the funds, it is a way to grow your wealth through equity buidup as well as income.
Hope the answer was not too confusing. If you wish to discuss in person - feel free to give me a call.