We are a real estate company that want to start with 360° tours. We have already a Nikon D800 with 14-24mm lens and tripod. What kind of system would you recommend for motorized head?
Depends on how much money you´re willing to spend and what featurs you definitely need. The cheapest solution would be a Merlin for around 500.-€ completely up to Panoneed, Seitz and Rodeon for around 2000.- to 4000/5000.- €.
For indoors the Merlin isn´t preferable becaus of it´s big base - the other heads produce only very small Nadir-holes which are easy to fix doing an extra Nadir shot or being retouched in minutes.
To be honest: for real estate indoors i´d suggest a good manual head and a fisheye. This way you only need 5-7 shots for covering a sphere. Your 14-24mm lens is a fine beast - but not ideal for doing spherical panos.
If you want something you´ve never had, then you´ve got to do something you´ve never done.