1. Temper their enthusiasm

Go slow at first. "Don't hire 20 people with disabilities if you've never been around someone with a disability," says Nancy Henderson Wurst, author of Able!, a new book about Habitat International.

2. Find expertise

Make sure at least one manager really understands how to work with people with disabilities. A person who has had a family member with a disability is probably a good candidate, says Wurst.

3. Do adequate screening

Interview prospective workers' caregivers because their commitment is crucial. "The biggest failures are with the family or the caregivers, not the employees," says David Morris, Habitat's CEO.

4. Team up with a school

Habitat has an internship program with the special ed department of a nearby school. The school is only too happy to share information and help with training.