To answer some parts of the question which are answerable as-is:
Yes, mortgage interest is deductible. So is depreciation. See this questionthis question and others.
It would be a good idea to put some money away for tax season, just as you should save some money to cover unexpected property expenses. But as @JoeTaxpayer says, this is a good problem to have, assuming you own the property, it's low-maintenance, your tenant is good, and your rent is at market levels.