how do you make garbage deals and stuff in this game?

you cannot be in cheat difficulty. The game never really tells you this so it took me a long time to figure it out. You also have to have:

For garbage deals: roads & rails leading outside the city. An arrow should appear.
For power deals: power lines leading ouside the city. An arrow should appear.
For water deals: Water pipes leading outside the city. An arrow should appear.

Also note that you cannot use deals on missions or contests, and you cannot make roads, pipes, rails, or lines where your land is at the end of the world map.

ps: This is the ONLY setback to using cheat difficulty, and I prefer the extra $800,000 over the small amount you make by having deals.