What kind of lens do i need to get next?

I'm a hobby photographer that has been moving more into doing it as a job, as i have started shooting more weddings and photo shoots. I have a nikon d5000 and i have an 18-55 mm lens and a 55-200 mm lens. I'm looking into new lenses and have considered the 18-200 and selling my others. Other than that what other lenses are absolutely crucial to have in my bag.

If you are going to be doing weddings, then you will need some fast lens.

The f/3.5-5.6 on your current lens are pretty slow.

Try picking up the 50mm f/1.8 (or f/1.4 if you can afford it).

For portrait and weddings 50mm and 85mm prime lens are very popular. And you don't have any prime as of now. Apart from primes, 24-70mm and one medium telephoto should be enough for your job. Try to get all the lens with maximum aperure f-2.8 and more.i.e f1.8, f-1.4…

The AF-S 18-200 mm VF lens would be a good single lens solution for shooting events. If you have a SB 700, flash diffuser and flash bracket, it should do all you need to successfully shoot weddings and other events

Later adding a AF-S 50 mm f/1.4 lens would certainly round off your system. Billing enough for your services will certainly provide you with enough capital to buy the equipment you need and feed yourself