This is a real easy cheat to get millions of dollars. First go and investigate 
a crash site, then when you finish it, research ALIEN ALLOYS. after its 
researched manufacture A LOT. when its completely manufactured sell it all 
because it costs 3000$ to make it, but gives you 6400$. You can also, sell all 
but one alien corpse. then, after you research it sell it. they give 
you 20 000$ each. 

This one is easy but sometimes can get frustrating and you MUST have a 
MEM CARD. When you start the mission, SAVE THE GAME. Then after 
you end your turn, if none of your guys die save after the aliens turn is over. 
continue until someone dies. when someone dies, ABORTT MISSION and 
LOAD GAME. Then do something different than last time. Continue to do this 
until the mission is over and none of your guys dies.

To manufacture for free, first go into the manufacturing screen. Pick 
something to be built. When the screen to allocate engineers and how many to 
be built, leave both amounts at 0. Then exit to the main manufacturing screen 
and select that item. Put some engineers in,(if it don't work like that, all of them) 
and make them build 1. IT WILL NOT WORK ANY OTHER WAY!