Yes, there's a fairly hefty maintainence tag on colonies... so if you over expand before you build up your economy, you will fail.

You only start out with 3000 space dollars, standard maintenance beta wise I believe is 25 dollars per colony, until you get some economic tiles in your lucky if you break even if you have more than 5 colonies to start with.

One of the fast ways to check that is to stimulate taxation, keep population under control, build factories first, trade areas second, research facilities third, with the food and ecstasy mob pleasers last after the economy has stabilized with trade in effect with other races.

Now given all this could change in 3 weeks when the game hits prime time you have to gage how your own system will work for you. This one keeps me in the thick of it more times than not, but not necessarily gets me a win every time at the intelligent / tough level of play with the beta AI which alas has taken to a life of solitude and is being fed soft food until a time when it can be put out to pasture forever. (hehehe thats about as PC as I can get)

W/R
Suralle Straykat
Kat Lord of the Pryde

Even in the Beta 5 release (which has larger colony maintenance costs) I found it best to aggressively colonizes the best planets before the other races do. I research the techs that help me build up my economy (factories, research, trade) and establish trade routes as soon as I get the necessary techs. By the time I get to the -500 billion limit I have a much larger population than the other races and hence tax base. I raise taxes and cut back on spending to not exceed the limit. As my income rises from my growing population and trade, I increase my spending and pay off the debt.

That's -500BC, which is the same threshold as GC1 had. Go farther in the red than that, and all non-maintenance spending stops.