You can draw up your own plans. It is easy. Just follow normal framing standards. (16 or 24 inch centers) For a portable blind, I suggest you use PVC or some other type of plastic pipe. For a permanent blind, use treated wood.
A recycling center (like for cans) might have some materials you can buy for cheap. We bought an old aluminum pool skirt for an above ground pool for next to nothing. We covered two of our blinds with this and then camo painted it. Additional fresh material is added before the season.
We built a few permanent blinds two years ago. I highly recommend you build them in your garage or on your patio. Some place level with access to power and a refrigerator.
We built each wall individually and bolted them together. Once satisfied, we removed two nuts and bolts from each wall join, stacked the walls flat on a trailer and took them on site. When on site, all that was required was a couple of socket sets, and everything was back together in about an hour. It is very important to use a sharpie marker and label each wall. You may think it is obvious which wall is which, but once you drill holes for bolts, you better know which wall is which and which blind it goes with.
I don’t think you can build blinds big enough. We store our water pumps, decoys, trap thrower etc in our blinds in the off season. During the season, we have enough room for all the gear, plus a dual burner camp stove. Two of our blinds are 12W x 8D. The other is 10W x 8D.
We didn’t build benches. We let everyone bring their own chair, and have quite a selection from stools to camo sling chairs to a small church pew. In one blind we have two old recliners with camo covers. Everyone teases us about that until mid day when the hunting slows down and then they fight like dogs to get one of the recliners.