Fairfax County provides real estate and car tax relief to citizens who are either 65 years or older or are permanently and totally disabled and meet income and asset eligibility requirements.
One of the qualifiers used is income. The gross income of the owners of the property (and any relatives living there) should not exceed $72,000. If you qualify, the tax relief ranges from 100% down to 25% based on your circumstance.
For requirements, go to http://www.fairfaxcounty.gov/dta/taxrelief_faq.htm .