question about income from house property

hello,

I read this nice post about calculation income from housing property. 

/forum/income-from-house-property-57074.asp

However, I had a question about an apartment that a person bought in the past financial in a city other than the city of residence using a loan. His/her parents live in that apartment so there is no rent. However, can the expected value of annual rent be claimed under rent not realized. 

thanks for your help.

momo