I'm only part-time in DC (part Boston) so I'm not familiar with the neighborhoods of DC outside of where I've stayed in the past. Is there an area of DC that would be considered the "financial district"? Previously, I've kept a couple small incall apartments in cities where I frequent and find the financial district of any city seems to do well for me.  

1- is there such a neighborhood in DC?
2- if this isnt the best place to host, any recommendations as to what part of the city would be good to get a small, but nice upscale apartment?
(I need to be in DC as opposed to suburbs because of my FT job, so two birds with one stone would be great)

I appreciate any feedback from providers or hobbyists. Thank you

As does ny.  For DC, check out Hamilton’s place

I guess the K Street corridor (from roughly 13th Street NW to 23rd Street NW) is the closest thing that DC has to a "financial district." The problem is that there isn't a high concentration of apartment or condo options along most of that stretch, except perhaps the western end (West End and Foggy Bottom, near George Washington University and Washington Circle, accessible to the Foggy Bottom Metro). This area would probably suit your purpose.
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The other areas of downtown DC with a good concentration of residential buildings are Dupont Circle, whichi is a 10 minute or so walk northeast of Washington Circle (and the stretch of New Hampshire Ave. between those two areas has lots of apartments and condos). Metro station is Dupont Circle.
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The eastern end of downtown, which includes the Penn Quarter neighborhood around the Archives, Gallery Place, and Judiciary Square Metro stations, has seen a good amount of residential construction in recent years.
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I think all of these areas would be good for an incall apt. Good luck!

What is your criteria for a small apartment?

I thought a lot about what you're asking, and DC just isn't built that way as strange as it may sound.

High rise? You'd have to be in Crystal City or Rosslyn for that.  
Super busy area, as to be discrete?
No doorman condo security?
Metro accessible? Easy Parking? (Easy parking and free excludes pretty much the whole city unless you own a house).
Nearby amenities? Restaurants?

There are some upcoming residences near the convention center and on Mass. Ave. near "G" street corner, kind of near Union Station.

A safer area is near DuPoint but traffic is absolutely horrific the hours you'd be wanting to host.

As mentioned, I'd target the "K" street corridor, but no lower than 11th Street. Then you're getting into the hood between 10th and 5th street area. Its being gentrified quickly, but not quick enough.

I agree Foggy Bottom or even just north of Dupont in the Adams Morgan area. Another area might be Capital Hill. Most anywhere in DC there is going to be traffic issues so keeping it close to metro is probably key.

Another thing, the city is filled with nosey little busy body political activists in everybody's business. Think Monica Lewinski and Linda Trip. They chased out the massage parlors out of DC, pretty much the vast majority of streetwalkers in the area, and you see most escorts hosting in Virginia than in DC.

Rosslyn/foggy bottom/farragut west/ dupont cirlce/woodley park/crystal city/tysons corner

in no particular order

Those are all affluent areas in decent neighborhoods (with public transportation/metro stops available for those wonderful customers who don't own cars, or don't want to have to worry about parking, license plate stalking, etc)

They all seem to have some nice hotels/restaurants/stores nearby and some of these locations are a little scenic, with the perfect setting...very pleasant for a guy to head out there and feel comfortable and have a good time with a sexy woman, not having to constantly look over his shoulder cuz who might try to do what to him in certain neighborhoods in DC or MD. (You know the ones I'm talking about.)

For those who are cheap and can show up a little early, there's 2 hour zoned parking on streets that almost always have spaces available and are an easy walk from the circle, for example on S Street NW and Florida Ave northwest of the Circle.