During gameplay, press CTRL + x to go to the console, type WeaknessPays, and press enter. You'll get extra money now.
If you don't like to cheat, simply be more careful with what you build. Every start of a new city can be a little hard, but you have to spent your money wisely, maybe even raise taxes a little. Don't spent too much on your policeforce, firebrigades, education and healthcare when your city is not yet very big. Make sure you have your settings straight.