Should I get work done on my house now or wait for spring ?
I need new windows and a roof and some wiring done that was corroded by the leaking windows
Everyone seems busy now as homeowners want the work done for winter so is it cheaper in the spring ?
If the windows are still leaking you need to get them done as soon as possible... otherwise you are just creating more and more damage to the structure of your home which will cost you more to fix.
Ditto on the roof if there is any leakage. Even if you don't see any signs of leakage on the underside of the roof, that doesn't mean that water isn't reaching the sheathing and rotting it away. Replacing shingles is a heck of a lot cheaper than replacing the sheathing/joists/rafters/insulation....
You say the wiring is corroded.... do you mean the junction boxes are rusted or is the insulation on the wires actually damaged? (Not sure how leaking water would accomplish this but...) If the integrity of the wiring is comprimised you should address it as soon as possible as you could have a potential fire situation.
Without seeing what condition your house is in, it is impossible to say whether you will save money by waiting until the slack time.
Also to be considered is that slack time for roofers is the winter and it's not the ideal time to be putting down asphault shingles, so you might be saving on the install cost, only to lose out due to a short life-time for the new roof.