Moby I think I get what you are trying to do - which is the same as some the business I have been focused on - Cheap, Quick, Good Enough.
Pick any new DX body (it really doesn't matter all that much if your focus is WEB.) The newest one's will give you the best latitude for editing though. Forget about not needing 24MPs - they are what they are. It is what comes with it that makes the difference and for that, the MP will be 24.
Nikkor or Tokina 12-24mm for interiors and large group photos.
35mm 1.8g & 50mm 1.8g for portraits.
Two - three strobes/flashes (sb-700 or 910s)
Add a few soft boxes for the flashes, cheap lighting stands (that go to 7ft), and a couple of books on lighting techniques on "business portraits" pick 1 style for lighting, learn it, and just do that one.
In all, you are going to should expect to spend about $3,000-$4,000 to get started from scratch. You will be able to use that set-up for 3-4 years and most of it for much longer.
I'm assuming you have a great handle on Photoshop so that will get you the rest of the way there with a bit of a learning curve.
I do agree with what others have said above, but business still are scrambling for money and most are bewildered by $500-1,000+ price tags for shoots that take less than 2 hours. I charge really low and am picking up business so there is a market for it as most pros just don't see the value in it. I look at it as, is 3 hours of my time worth not getting paid or getting paid?
Reality is, if it is only small web files, much of our understanding of photography is unfortunately lost in the end-use. Basic Head-shots are relatively easy with a bit of practice. Interiors can be very difficult but if it is just a "documentary style" where color, textures, etc. are not important, then that is easy as well with practice.
I do find it disheartening that people do not want to pay for the "pro" and don't understand what comes with it, but at the end of the day it is about managing expectations on both ends. Sometimes the end customer's expectation is do it for very cheap cost, and the result is what it is. They understand it will not be as good, and they fully accept it. I have worked for many companies that viewed it that way and said (in back rooms) "to hell with what the professional thinks we need." No salesmanship will get past that. On things they deemed it mattered, they had no hesitation to spend the money for the best result.