What is your intended use?
What do you mean by 4k ready?
You can buy a i3-6100 for $125, a lga1151 motherboard for $50, and 8gb of ddr4 ram for $35.
Check the specific motherboard, but integrated graphics can run 4k resolution.
Not at fast action gaming speeds though, more like 24hz.
That makes you ready,
You can go up from there with a stronger graphics card.
Here is a review of the i3-6100
http://www.anandtech.com/show/10543/the-skylake-core-i3-51w-cpu-review-i3-6320-6300-6100-tested