If you are serious about progressing as a professional, and your intention is to have a sucessful buisiness, then I think just about any investment toward that goal is worth it. Just be careful to weigh your cost of doing buisiness against the money you're putting into it. Most "up and coming" photographers are actually loosing money. Depending on your business situation, it may even be something you can write off as a business expense. Personally, if I was in your situation, I would probably just save up my personal savings until I could pay for it outside of my buisiness costs, because I would look at a new camera body, that is helping me to continue actually learning to be a professional photographer...as sort of a half buisiness half personal expense, and a "start up" investment for my goals. (Just like any lighting, insurance costs, web development, marketing, etc.... would be when starting a new buisiness.)
Anyway, take it from somebody who has been using the D5000 and the nifty 50 pretty much exclusively since I started on this venture... It's a decent little camera, and it can take you a long way. But I will admit to being "held back" on many occasions due to its limitations, and I think a full frame camera, with commander mode, high ISO capabilities, internal motor, among many other bonuses would be invaluable. Granted, there are plenty of other things that are JUST AS invaluable, here's a short list:
-good knowledge and practice of "seeing" light. You can utilize this in so many creative ways with outdoor "natural" lighting. It's trickier, and will often limit the locations you choose to shoot in..But it will also make you more creative, and purposeful with your photography.
-Any off camera flash, and a good knowledge of how to use it. Yes, I know...I love working with natural light only..But I have learned that in those situations where it's so dark that you're wishing for a higher ISO camera, it's more likely that an OCF would give you a better result than bumping the ISO on any camera body. You can make the "grain" work to your advantage on any camera that you've raised the ISO on, when you're using good natural light in the right way. Maybe you've seen some of the beautiful black and white conversions on pictures with all natural light, with lots of grain...it gives it sort of a nostalgic feel. But if you have a high ISO performance camera, you're wayyyy more likely to just say "ah what the heck..I"ll just raise the ISO" in situations where you *could* have used the light much more wisely and gotten a much better shot with a lower ISO. I could definitely see that being a trap to fall into if a photographer's first solution to "being held back by low light situations" is to get a camera that will shoot at higher ISO's.
Also..along the lines of using flash...it really can look natural, especially in those low light situations. It doesn't have to be overpowering, it can be subtle. It can fill with just that extra bit of light that you need to expose the scene. I have taken some shots using my "pop up flash" because it was all I had. I would just hold a card up to the base of the flash, and angle it so my light would bounce off in the right direction, and create some soft, extra ambient light, so I could still get the look I wanted. You could probably get even more creative and precise with the use of a good OCF, or just a nice speed light and bounce card.
These are some older shots from last year....but they show what I mean about bouncing my pop up flash with a card, and still looking like natural light. These were taken in a DARK room. I mean pitch black dark. There were only a couple of candles on the wall, at night in an old schoolhouse...so the "natural" light in that scene would have needed to be shot at about ISO 3500 minimum, and the candle light would have cast odd shadows on my subject.
This was the pop up flash result:
I'm not showing these to say LOOK I'm soooo awesome by any means LOL. These are older pictures, and I know they have issues. (Red lobster skin on the groom much? haha). But, to me, they show that even a basic pop up flash can create soft, directional lighting that mimics the effect that I love about using natural light. And it didn't cost me 2,000+
Anyway..I guess what I'm saying..is that if you feel like a better camera would help your business, and it doesn't hurt your business to make the investment, you should go for it. But just don't overlook the other, more simple and less expensive, alternatives before you make the plunge. I really believe that it's worth it to come to the point where you feel that you've mastered the simple things I listed above, before you look for new equipment to solve your problems.
P.S. I would probably have personally taken the plunge and bought a D700 several months ago...but I ended up choosing between a new camera or a violin bow that wasn't well...broken in half lol. The violin bow was a bit more of an urgency
