I'll toss in my agreement with inparadise and Dave. Go ahead and get the mortgage. It is typically easier to do on a purchase rather than a refinance later.

Further, if you were to refinance to get a mortgage some time after purchasing, you run the risk of only being able to deduct the interest expense on $100k of mortgage - and not even that if you are subject to AMT.

By getting the mortgage now, you are keeping your options open. You can always choose to pay the mortgage off at any time in the future. But you might not be get a loan in the future if you need to.

--Peter