Re: rental income - this is an IRS rule - you can book 14 nights income tax free per year. But I do not know if you have 2 units, if you can book both units for 14 nights per year and do so tax free? You would need to consult a tax advisor if you cannot find the info online. Be aware that you cannot deduct any expenses for those 14 nights.
But consider this...if you book 14 nights in 2017 at one home, I believe that you can book 14 nights at a different home in 2018. The rules generally apply per year.