Realize that the Treehouse Villas were built several years ago, long before the American Disabilities Act surfaced.
They are now required by the Federal Govt. to offer a certain number of units in order to open them to the public. Based on percentage of overall number of units, they had to pick the 4 units that were closest to the main road. The ramp is extremely long, but not steep - it has to comply with the 1:12 slope (1 inch slope for each 12 inches of ramp). It offers a "resting" point, about halfway through, again required by law, and actually set it up as a place for a picnic table and chairs.
But you may want to look at the pictures of the ramp leading up to the unit, just to give you an idea. Don't expect to be nearly as close to the main road as you may expect....