unless you got a monopoly or you collude with the only other big farmer there should be no way to benefit from making a buyout against a game full of rational players. Most countries are governed by irrational players or bots(no bots on primary) tho, both of which can be taken advantage of.
I have only benefitted from my own buyouts on rare occasions on two servers. Primary is not one of them. It's generally a bad idea and most people lose money in such ventures.