As Alibaby suggest I would recommend putting a set amount of money aside for a few months and start researching the various products on the market.

Also look at second hand cots, tallboys change tables etc so you have an idea of what they retail for second hand. You may be able to pick up something thats practically perfect that is a second. I would suggest buying new mattress and linen though but thats just me. All my furnishings are seconds and seriously you couldn't tell.

My nursery has been set up and re arranged 3 times since Nikita died. DH and I have only brought a baby monitor this pregnancy - we are waiting until we get to 30 weeks before we go too nuts on linen and stuff, we are a little paranoid though given our history.

When is the right time?? Essentially thats up to you the right time is different for everybody.