I too am curious to know why a rise in price is perceived as a problem.
Use as a medium of exchange is critical to Bitcoin's long-term success. Instability in value makes a currency harder to use as a medium of exchange. Imagine, for example, if you placed a large purchase on a Bitcoin credit card and the value of Bitcoins doubled. Or imagine if your rent was in Bitcoins and then the value of Bitcoins doubled.
Part of using something as a medium of exchange is you hold those things to plan for future purchases. If you're paying rent in BTC and holding dollars, you're doing it wrong imo.
Sure, that solves the problem for people who have enough wealth stored that they can stash the money to pay all their future rent when they enter into the rental agreement. However, for ordinary people, having their rent suddenly cost twice as much of their income would be devastating.
To me having 6-12 months of rent saved seems fairly "ordinary" when you enter into a rental agreement. (I'm sleeping in the woods before I'm coughing up like most of my net worth on rent.)
But regardless, I don't think it makes much sense to make long-term contracts in BTC
right now. Your hypothetical person should be getting income in BTC if it makes sense to do rent contracts that way.
When it's widely used, then it can be stable, but stability
now would just mean bitcoin is never widely used.