Hi this is kind of a cheat but not exactly.
To keep rat levls low, get a radiator or drink machine and place it in front of a rat hole, you can keep it there or you can move it back beacause it will be gone.

I've only tried this once because me and my friend were trying to do some fun stuff on Theme Hospital. We found out that Receptionists never go to the staff room. That's kind of boring so we picked one up and put her in the toilets, she went to walk out but then disappeared. We then realised that any patients who tried to go to the toilets would get stuck in the doorway and wouldn't be able to go in. They would walk up, stop and then keep moving their legs! It doesn't really help much but it's funny to watch.

If all you have to do is get some money to finish a level, and you don't want to properly cheat. Then click the dollar sign in the bottom left corner take out a massive loan and then when you complete the level you don't have to pay it back!

As we all know, the machines in your busy hospital occassionally break down, or if not properly maintained blow up!

Make sure that there is a fire extingusher in in each room, even better put it right next to your machine, for some reason they are much more hard wearing and need hardly any maintainence.