You might want to check with Harry "Hally" Alliandes because he looted several Lost Pages on Toulan and I think he has sold an apartment or two, and he might have one he may be willing to sell. I'm not sure what the average price of a Toulan apartment is though because I think only a few have been sold, but I also want to say that the cost also depends on whether the apart is small, medium or large.
Another thing you might do is check shopkeepers either standing at booths or in shops to see if a deed might be available because I've seen a few of them this way too.