Well it all depends on what brakes you going to put on the bike.
If your looking for a set of maggies for it, then brand new your looking at £100 just over really. But then second hand and it could be half the price, depends what mounts and pads you want. You can buy standard maggie mounts around £20 and pads range from £10 up to around £35ish.
Getting the brakes on the bike won't be an issues as its just a few bolts but if they needed bleeding then will be a little less simple. But thats what the forum is all about to help riders out so few tutorials and your on your way mate.