How to connect a city and a rural business?
Well, it is not much different from connecting cities to each other („How to edit an existing city?„). “How to create a map in an at least somehow balanced state?” already has some advice regarding the balancing. In other_templates.tmx (background image) there are two layers called G0-2-3_G1-2-3_G2-1 and G0-rest_G1-rest_G2-1 which indicate radii for connecting rural businesses to cities. For both of them, the centre of the circle should be on the city centre and the rural business‘ centre should be located somewhere within the circle. However, if you decide to connect a city and a rural business to each other of which the rural business is outside of those radii you will still be able to do it, but you should not take the exchange of commodities into consideration in regard to the game’s balance, as due to the extended distance for traditional commodity transport there will be a supply shortage.