I would recommend doing the quest to obtain the treasure (a diamond larger than a bloody melon) in Aurora - you are notified of it by the greedy bloke who stands in the treasury (Hobson? I believe) and keeping it to greater serve Albion with your profits. It will net you only a minimal hit in morality, which I didn't like seeing as how my intent was to reap greater rewards for the kingdom all along. The diamond is worth 700,000 but couple that with what you may already possess in the Sanctuary, buy every property you can get your fingers on, and you will be scooping in one-hundred thousand every five minutes.
My first play-through (roughly fifty-five hours to the attack); I made every decision to benefit the people and respect each promise and still managed 7.5 million in the treasury, and a couple hundred-thousand in the sanctuary, by the time the attack came.
Though, now I confess a bit of disappointment in not seeing more effects of my completely sacrificial and ethically pure choices throughout the game. Gaining a guild seal in appreciation from every person I walk up to is nice. What use is tens of millions now? That was to be expected, I suppose. My last lady in Fable II had 26 or 28 million to do absolutely nothing with except give fifty or one-hundred thousand to that poor fetcher who sits on the bridge in Bowerstone Market each time I pass through.
Oh, and glad to finally make the decision and sign-up here opposed to my long time of lurking around as a guest.