Most startup offices don't have wheelchair ramps. Just take a tour of the offices on castro street, home of startups like Mozilla, Meebo, and Outright. Most of those buildings have restaurants on the ground floor and offices on the 2nd floor. Most of these offices don't have ADA complaint bathrooms either.
What happens if you've got an office with 15 people and then one becomes disabled, or a strong candidate (who you'd otherwise hire) is disabled? Retrofitting may or may not be feasible; moving offices sucks. I'd be tempted to do wfh/offsite, but that may not be adequate for ADA reasons or civil lawsuits.
