meh, 10 to housing is not a bad income with the rest in agri. 30 for RT probably if you want to really concentrate on it.
on normal, i got 20 housing, and the rest agri, and i still make better income long term going agri than i do housing. Even when food was selling at 5 and 6 on normal server a ways back (it`s getting to that point again now), before the update, i made better money than plunder long term.
Best thing to do is, keep about 1.5 billion cash on hand at any given time, and save up the food until it goes high again (which it always does at some point), and then sell it.
Then you`d have like 700 million food to sell at like 15 or higher (in small loads, of course, not all at once), and you`d get oodles of cash. Only sell below that if you *really* need the cash and you`re low on reserves or something. As collective, you *really* don`t need more than a couple billion to play in the high PR levels unless you have a nasty habit of keeping terran or a miner ships for a lot of turns (in which case, the upkeep WILL kill you :P)