At any time, hold down the 'SHIFT' key and type "FUND". This gives you an extra 10,000 smackers. It also causes an earthquake every tenth time you do it, so do it before you start your city. In some versions this only works when on the title screen and not during the game.
Another cheat is to set the citizen's taxes to 0%. Then just before tax collection (December or November if playing at fast speed) quickly set the taxes up to 20%. Then after you collect taxes, put it back down to 0%. This way the citizens think they are not paying any taxes.
You can build land on water. Find a straight (horizontal or vertical), stretch of coastline and string a powerline along it. Next, move one square over, out into the water and string another powerline parallel to the first. Repeat as many times as you want. Then just bulldoze all the excess powerlines and you can build on the new land. To make land you simply make a 3 lane highway across any water source. When you make a road by putting 3 sections of road on top of three section of road on top of three sections of road (3 by 3) you make 1 section of land in the middle.