Depending on your budget, having a PC where you can both develop and test the game without unrealistic expectations of user hardware is a good way to go. If you can afford it, buy a class rig. But just remember you need to be able to test the game on a viable system, something a regular player in your audience would have. Generally something mid-range is sufficient since UE4 has a lot of player options for optimizing performance right out of the box.