I will be honest though. Monthly profits is not where the strength of enterprises exist. Top-end performance will eventually lead to crushing amounts of enterprise tax. The best attributes of an enterprise are these.
1. You need them for game level, and the coins that come from them.
2. They store weapons at no cost.
3. They refresh a full $500 Billion in spending limit each month. Sale on this product or that? Buy low now, sell high later, when the market recovers. Every CEO who boasts how much cash they have does this.
4. They offer the utility in assisting your countries economy in a few important ways.
-They allow you to train your max housewife numbers while still maintaining control of the enterprise corps you host there.
-If you go with public, and especially truly public corps, they offer the utility of an extra share buyer/holder in these corps.
-Not sure which boosters to buy to extend your enterprises? No problem. Simply stock up on super boosts, and put your enterprise in charge of building and instantly upgrading a few corps for your country. Already at the 20 corps limit? No problem, have your country nationalize one. It happens instantly (within 10 minutes or so in the same game month) and then you can build or simply relocate an already upgraded corp there.
5. Beyond simply storing weapons, enterprises offer extra utility during war-time, if you happen to have an account that spans multiple worlds. Having a local enterprise on a given world means that you can store a reserve of weapons near the action (again at no maintenance cost), ready for a short shuttle ride when you need them.
The above attributes are why I keep my enterprises around. In monthly income, my countries make my enterprises look absolutely silly.