I've done this recently, and am currently in the process of moving -- getting rid of all our furniture and doing it all again. You definitely do not need 6k-12k to furnish a place. My recommendation for you, if you've been without stuff for a while (as I was for about 4 years before getting a permanent place again) is to seriously rethink how much furniture you need.
Dressers? nope, don't have enough clothes for that, just got $10 hanging shelves from Walmart.
Desk? I always had one, and never actually did any work on it. I just work from the couch.
Bedframes? Why? Just one more thing for my toddler to fall off of.
Mattresses are cheap these days, I love my Allswell mattress from Walmart.
We have a playroom that has no furniture at all in it, and it's perfect for my son. I'm not sure there's an age where that won't be true.
Ballpark, we spent $1500 all-in to furnish a 3 bedroom place. My guess is we'll spend about the same on our next place. We're planning to spend more on a couch this time, but won't have to rebuy anything that we can fit in our car for the move.
We bought every single thing on the internet and had it delivered. It was all very easy.
Another consideration -- furnished options are not only more expensive, but the selection is very limited. If you go unfurnished, there's a much greater choice of area, etc.