Today was a telling day in housing.

While the National Association of Realtors pending home sales index hit a seven-year high, Freddie Mac announced the 30-year, fixed-rate mortgage posted its largest weekly increase since April 1987. 

These two reports suggest the clock is ticking for homebuyers wanting to lock in at low rates. The 30-year, FRM came in at 4.46% this week, up from 3.93% last week and 3.66% last year. That’s a significant jump in a very short time. 

Does the 6.7% increase in NAR’s Pending Home Sales Index indicate a bottleknecking of sales as buyers rush to get into a home before rates rise even higher? 

And the even bigger question is: At what point will the rates get so high they begin to squash sales instead of fueling them? 

Fannie Mae Chief Economist Doug Duncan said once rates have risen to a certain point (100 basis points from the time of the interview), home sales may begin to slow. 

Sterne Agee Analyst Jay McCanless is afraid home affordability could decline if rates edge much higher, curtailing gains in the homebuilding segment.

But what’s important for buyers to remember is that these rates are still low — at least compared to the days of 14% and 15% rates. If buyers panic and push to buy now, it will only eat up available inventory, pushing prices higher.

With affordability becoming more of an issue as rates rise, this will make it nearly impossible for buyers — especially first-time homebuyers — to get into a home. 

Zillow’s [stock Z][/stock] director of Mortgage Marketplace, Erin Lantz, expects to see more fluctuations, including additional rate drops.

The takeaway: the market is volatile.

A good move today may seem like a bad decision tomorrow. Ultimately, it comes down to whether a potential buyer is ready to bet on today’s rates.