Inflation has a minor effect too.<p>The $300K is fixed for the purchase year but the expenses are not. The inflation-adjusted expenses of $12,000/year corresponds to $6-$7 of the $50/month increase.<p>($12,000 / 3 / 12 = $333⅓ per apartment per month. With inflation around 2%/year that's $6⅔/month.)