Count out the size of the property you own in the city, then buy a plot in /warp creative and build a house there that would fit on your plot on the city. For example, if h101 is 15x15 blocks, build a house in the creative world that is 15x15 or smaller. All buttons, trapdoors, and blocks in general must fit inside the border.
There's no official company plugin at the moment, so to create a business just advertise it in chat or here on the forums in the "Market Place" section. There's no special rules/regulations for businesses (you don't need a headquarters, you don't need a specific amount of employees, etc.), just follow the server rules.