When I say four thousand houses in Spanish, is it gender dependent like cuatra mil ollas or do I simply say cuatro mil ollas. I know the numbers from 200-900 are gender dependent but I'm not sure when you get to the four in front of thousand

the numbers are not affected by the gender of the noun in this case.

BTW, houses = casas. ollas = cooking pots

cuatro mil casas, cuatro casas, cuatro ollas, etc..