Hello,
I am purchasing an older house (built in 1985). It does not have GFCI outlets and the inspection called this out. Is adding GFCI outlets as simple as replacing the outlet with a new one or is there re-wiring involved?

As long as there is a ground wire present in the box, you hook black to the brass screw, white to the silver screw and green/bare to the green screw. It is quite simple.

~Matt

And, if the house was as recently as 1985, then you almost certainly have a three-wire system with which to work, at least if it was built in the United States.

When changing standard receptacles to ground fault receptacles, and the wiring is going from outlet to outlet,care must be used to note which set of wires in a box are live, and which are load, or feeding the next outlet in line.

If there are only one set of wires, black, white, and green or bare ground, then connecting is as simple as the previous answers. However, at most outlets you will find more than one set of wires or cables.

Each GFI outlet will have a set of terminals labeled Line and one set labeled Load. There will be one set of cables feeding the outlet. These must connect to Line on the GFI. If there are other wires continuing onto the next outlet, these may connect to Load, if you need the outlets downstream GFI protected.

The inspection report should have identified the areas that are now required to have GFI outlets, all kitchen counter outlets, bathrooms, outdoors, garages, and unfinished basements. Any outlet in these areas that are for stationary appliances, such as refrigerators, freezers, sump pumps, garage door openers, etc, do not need GFI protection.

Where I live, You have a New House.
You may be able to install GFI's in Panel. Be careful installing on circuits sharing a neutral.