I am moving my hot tub to my new house and I don't have a empy spot in electric box for anymore breakers and it's a 100 amp box they say I need to upgrade to a 200 amp box for about 1,500-2,000 any suggestions?? And the house I live in is not that old it was built in 2000 they just used the cheap way and put a 100 amp box in on the outside of the house!

What else is electric in the house?
How big is it?

I will almost guarantee with a house that new you will need to upgrade to 200A. A 100A was probably barely legal as far as the load calculation goes.