Here's my two cents, and keep in mind it's only one perspective of a few.
For starters, TurboTax is a bear when it comes to fractional sales of real estate. It can be done, but it requires a lot of manipulation and manual math on your part, thus greatly increasing the possibility of human error resulting in an audit. So in my opinion professional help is not an option - it's a must.
Since this involves rental property, this sounds to me more like the establishment of a partnership where you have a family member "buying into" your rental business. That opens an entirely new can-o-worms on the tax front, as a partnership between two unmarried individuals not filing a joint tax return together generally calls for a completely separate 1065 partnership return to be filed. (Although with rental real estate, that can sometimes be avoided by reporting your percentage of ownership on the SCH E if your state and local laws don't prohibit it.)
Because of all the different "points of view" one can take on this, I would suggest you seek getting educated on your options not only by a local tax professional (especially if your state taxes personal income), but also by a real estate professional. Generally though, I wouldn't expect a real estate professional to be that knowledgeable on the tax front. But if the family member will be taking out a mortgage for their half, it will definitely affect you (and not in a positive way) should that family member default on the mortgage.
As an example, if they default on the loan, the lender may not foreclose on half the property - they're foreclosing the whole enchilada.
