Right there with you guys on buying secondhand. I hate to pay full retail. I prefer to buy things used, private party, and preferably broken... for scrap prices.
I don't do thiftstores much, they mostly just have household crap, which I have enough of.
Definitively use habitat restore.
Here's an example of my most recent endeavor with it:
Right now I'm putting down oak floors all through the house - from habitat. They had pallets of mixed oak hardwood. All different finishes, some unfinished - but all new, and for $1 per square foot.
Different finishes is kind of a problem.
So, I found an industrial drum sander for sale. 7.5HP Baldor motor, 36 inch wide infeed. It came from a small one or two man cabinet shop. The owner had purchased it used from a machinery dealer. It worked okay, but didn't look great - so he had an helper tear it all down and paint it. Replace bearing, etc. The helper quit midway thought the project. I brought it home in buckets. I did have to do a little machine shop work on it, but she runs great now. The flooring comes out of the machine beautiful - ready for stain and poly. When I sell the machine back off I'll stand to make a decent profit.
I've got one room and the hallway done. We started the second room today. The floor looks good.
Sure, I could have paid someone to come in and do it. Maybe about twenty thousand dollars? DIY, I'll have three thousandish in it. And a ton of time. And effort. That's okay, because I value and pride my work, seeing what I've done, and I also value saving money. I want that money to do other things I want to do.
Not everyone is like that, and that's fine too. Lots of folks want to work their one job and use income from that to avoid other work. I work with some people that are happy to pay someone to cook for them, mow their lawn, clean their house, etc. It's what they value, and there's nothing wrong with that... but it certainly isn't what I value.