The factor you missed to consider is that all investors are greedy. They will always try to rent the house using market rent. They will not base rent on their mortgage payment. For example, if their P.I.T.I (Principla, Interest, Tax and Insurance) is $1400/month, they will not rent out at $1400/month. They will always check with MRIS to get the market rental rate, currently $1700/month. They are happy to retain the profit of $300/month. In some cases, in order to increase competitiveness, the investors can reduce rent by 50-100 to rent out. However, not everybody will do so.

The only reason that a landlord will reduce rent is when there is a over supply of rental units in the market. This is not the case in current market. Many potential buyers are deferring buying and turn to renting. As time goes on, more and more people defer buying, and less and less people become landlord due to fear. Rent may even go up instead of drop.

However, in a deep recession, total number of jobs will go down, causing people to move out, however. DC area has always been an economic magnet for nearby regions. If DC metro experiences recession, Richmond, Baltimore, Philadelphia, Harrisburg, Virginia City or even Pittsburg will experience worse recession. People from these cities will migrate to DC area for better opportunities. In that situation, even if DC has less jobs, people will move in more than ever, raising the demand for rental units.

Therefore, your worry is unfounded.