As you can glean by the other answers, deductibility comes with conditions and will not last as long as you will probably be in the home. So, what are your options? If you have less than 20% down, here's what you have:
Do a 1st & 2nd combo ( we will do up to 95% ) and you avoid PMI.
Finance the PMI, 10% down will cost you about 1.5 - 2%(based in part on credit score) of the loan amount and it will be added to the loan but, will not be added to the loan to value for qualifying purposes. This will raise your payment a couple of bucks a month and of course your interest is deductible. Some lenders will allow fincing the PMI up to 95% but, as you may imagine it does get costly.
You can pay the PMI up front as a closing cost and then you avoid monthly PMI and the cost becomes deductible in the tax year that you close on the home. Abou the same cost as financing.
Those are the options and based on your own circumstances; its up to you to choose the most viable.
John P. Thompson