Here is my 6.5' x 10.5' fish house build step for step for people looking for info like I was/currently am and looking to spend under $1000. Since money is a factor it wont be a drop down. Criticism is welcome. I bought a 1969 Bethany pop up camper from a guy off craigslist in September for $120. I stripped her to the frame and began building. The frame wasn't complete so I went to Winnicks in Forest Lake and bought 24 ft of 1/8" 3 x 1 1/2" steel tube to finish welding off the frame. Had an angle grinder with wire wheel to get rust off and welded it all up. Then I ground down the top and outer welds flush to make it look good and so the plywood floor would sit flush. Then sanded the whole frame and spray painted a couple coats of gloss black Rustoleum paint. I got my hands on some scrap 2" extruded foam insulation so I used that for the floor. I cut it out to fit between the frame pieces. Then I sprayed some can foam insulation where the foam met the frame on the top and bottom. That stuff really glued it in to place! I trimmed the top off flush with the top of the frame with a knife. Then I bought 3 sheets of 3/4" treated plywood and cut to fit. I attached it to the frame with tech screws rated for treated plywood from menards. I picked up some 3'x10' sheets of steel siding off craigslist for under $10 a sheet and have a bunch of longer scrap pieces of various 2x4 , 2x6, and 2x8 pieces of lumber from a garage tear down this summer. So here I am. I'm thinking of ripping my lumber down to a nominal 2x3 for the studs and putting them 16" on center then using 2x8 for the roof. Ripping them down from the peak for a sloping roof. Going to use fiberglass insulation for the rest. Looking at a nuway propane heater and going to run led lights and radio off 12 volt batteries.
I got my walls up and windows in. My walls are 2x3's 16" on center all screwed together and the bottom plate screwed every foot or so through into the frame. I picked up a 2'x3' window, a 2'x2' window and a 80"x36" exterior door for cheap. Here's what she looks like so far.
I put up my roof over the last week. 2x10's ripped down at an angle to 2.5 inches on the end. Going to start siding and roofing here in the next couple days. To stabilize it I'm just going to use wood blocks stacked up. They're already pulling out houses on Red so I better get going!