Hello. I saw you were thinking about trying a flight sim game with keyboard and mouse. I understand money issues being a poor person myself but flying with keyboard and mouse is just horrible.
The main reason is because with keyboards you are have to choose between all or nothing, or graduated steps. By this I mean either full turn, or you push it 1-2-3-4 times for 25% movement and then push another button to go 25% back the other way in steps.
With mouse, you will be missing one of the 3 flight controls. With airplanes you use the rudder for twisting the nose right and left. the airlereons to tilt the wings left and right, and elevator to pitch the nose up and down. This means at least one will have to be keyboard controlled and you run into the above paragraph.
This said, you will really want to consider a joystick to be able to enjoy a flight sim. If you woud like my personal recommendation for an affordable and well constructed joystick, it would be the Saitek Av8r. I have one and I've been quite pleased with it. I've had it for years and in that time it's both been mostly inactive (and gathered dust) and hasn't required any maintenance when I want to whip out my joystick. The only maintenance I've had to perform was taking it apart due to the grease inside becoming spoiled/wore off from use.
One thing to note is that it has rudder function by having the stick being twistable. This is most excellent and saves money due to not requiring rudder petals (or keyboard use otherwise)
I recommend it mostly due to cost however. I think it was 20-40$ when I bought mine as I doubt I would spend more than that and it has served me well for years and was well worth it to me.
If you can find a newer model for a good price get that instead though; it looks like it's not manufactured anymore. Just make sure it has a twisty stick or whatever the term might be as that will save you money or frustration. A good idea is to get one with as many buttons as possible. Av8r for example has the switches at the bottom which all function as seperate buttons in the up/down positions. It's useful in most games; such as spaceship and flight sims as generally even the simple ones will have viewmode switching buttons you could map.
Also it would probably work well in a tank sim due to to twisty stick(I think you mentioned one of those back when you used to play Illyriad) but maybe not as well as a mouse if you are already used to that.
Here is a link I found real fast after a google search:
http://www.amazon.com/Saitek-Aviator-Throttle-Joystick-PS33/dp/B000I62PEK