First off you'll have more options in every aspect going to a 7mm WSM
over the 270. 270 is a token round because people like it for things other than the realty of true performance off and on the bench. You can see that clearly on this forum, almost no one runs a .277cal bullet but there is hundreds of flavors of 7mm.
Second, you're pretty much stuck in the $700-$900 range for a complete bargain set up that will do the job. From my experience I've spent hundreds of dollars trying to make something work and in all honesty I could've purchased my dream rifle from the money I spent trying to cut corners.
Do your self a favor. Save some more money and get what you want. I finally did it and now all I do is think about how much I flushed down the toilet.
If you need ideas of how to put a gun together by pieces for the lowest you can then ask that. I'm sure you'll get tons of help of how to do that.