House Sitter in Washington, District of Columbia

I run a small international development non-profit organization and need to spend several weeks in DC in either March or April and would like to house sit for all or part of the time in order to minimize the cost of my stay. I am a home owner myself, married, mature (well- at least my hair is getting grey), well educated and extremely responsible. I am an avid gardener at home and so can care for plant. I can even pet sit, provided your pet can be alone up to 8 hours a day while I'm at meetings, etc. DC, MD or VA would be great as long as its close to public transport to downtown - since I'd rather not have to rent a car. My dates are pretty flexible right now since I'm trying to book my visit around when I can find a reasonable place. Thanks!