Well that depends on how complex you want to get. Reason (from what I saw on their site) looks like a pretty full featured program, if you merely want to put something in so you can work with it a little, you need not spend any money at all:
Power Tab (
http://www.powertabs.net/)
-Simple little tablature program, kinda clunky, cost = nothing.
Finale Notepad (
www.finalemusic.com/notepad/)
-Program similar to sibelius, free.
Guitar Pro (
www.guitar-pro.com)
-Similar to powertab, but better. I have this and use it to write down ideas, works beautifully so of course you must buy it ($60) However, version 5 is coming out Nov. 20th so wait until then if you are interested . (Demo available)
Hopefully one of those will suit your needs
