I've discovered an interesting strategy based upon using Terrans in DA with Super Diplomat and maxed out diplomacy. It goes something like this:

Step one: research rush. Get Diplomatic Translators as fast as possible, along with some tech for trading while the treasury still has cash.

Step two: trade like crazy. Get tech, planets, and lastly, cash (to postpone the inevitable red zone).

Step three: keep trading for planets until your influence covers 75% of the map and you win.

Works best with lots of opponents (so a few techs can go a long way), and lots of stars/planets scattered.

I think it's crazy to win with -7k in the bank. (my record was over 30k in debt at the end of a game on a huge map)

Some things I've learned:
1) possible exploit: It is possible to buy buildings on planets even when deep in the red if you use the colonies tab of the Civilization Manager.

2) Leases can be useful for speeding up the start. By the time the total cost reaches the normal cost of buying, you should be so far in debt, it won't matter.

3) Having a planet focus on social or military can usually squeeze at least 1 point of industry out as long as spending is set to 100%. In my Experience, my Home world was able to get about 8 points of military giving me a constructor (for upgrading my mining starbases) every 20 turns or so.

4) Creativity can make it possible to slowly get some research done even when not spending any money on research.

So far the highest difficulty I've used it on is Crippling, though I did set Habitable Planets, Planets, and Stars to abundant, and Star Density to Scattered. I also had 9 opponents, and 8 minor races. I always like to use the Pacifist Party for this, since ultimately I'm relying upon Influence to win.

Has anyone else tried playing with their wallets in the Red for most of the game?