Are there any companies in US where I can get a cheap router or building kits? Working area at least 12 x 12 inches and up to 12 x 25...

Try harbor freight. No the best quality, but it may work for you as a starter. I have one kind of like this, and it works ok for routing and triming.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=44914

Sorry! I meant a 3 axis router for cnc projects. I couldnt find any on that site

You mean make your own. I thought you meant you wanted one to add on to to a home built kit.

you can get the plans for free. What's your definition of "cheap"? Actual built will vary depending on what you use, but for the most part in the end there really isn't any cheap CNC that'll be a decent quality as well. $1000 easily IMO for an average 1st time usable CNC build.

We have a 25" x 12" ( working size) CNC router in stock if you need it ($1699 + shipping), email me at support@kelinginc.net. Or see our CNC package:
http://www.kelinginc.net/CNCNEMA23Package.html
http://www.kelinginc.net/ControlSystem.html
http://www.kelinginc.net/CNCmachines.html