A running toilet is a quiet drain on your sanity and your water bill. Upgrading to a modern gravity flush model takes about two hours of plumbing work, but it saves you years of jiggling the handle. Late winter is usually the best time to do this, as plumbing supply stores run clearances to clear out inventory and local plumbers have lighter schedules.
The toilet itself costs about $400. Before you buy, call at least three local plumbers to get installation quotes so you do not get hit with surprise labor fees. We can also time this with a specific credit card to spread the cost out without paying extra.
The catch is that the 0% rate is not a permanent discount. If you still have a balance after the 18 months are up, the standard interest rate kicks in on whatever is left, which makes your cheap upgrade a lot more expensive.