I suppose that a tiny-house is built to a similar size of an RV and has wheels like an RV, so that it can be legally positioned on most any lot. And a tiny-house on a temporary foundation and with wheels, can be a heavier construction than an RV because the tiny-house doesn't really need to be an RV but just appear to be an RV so that it can be legally parked.
Or I have seen many tiny-houses on remote lots built on permanent foundations. It's just one genre of news-reporting that defines tiny-houses like parked RV's. There are programs on cable-TV that feature tiny-houses on permanent foundations.
Now I know of a set of permanent building constructions that are easy to build because the foundation is easy to build. Basically, just stick a piece of 304L in a wet-pour concrete footing and that's the foundation.
These foundations are crawl-space foundations. For instance, a 2" to 2 1/2" diameter 304L round or square tube with 0.120" wall thickness, should be cut to length, have a 304L flat plate welded to the bottom, and have a 304L L-angle welded to the top. Then a floor-joist-end and a stud sit on the L-angle and bolt to it. The floor joist and stud likely sit side-by-side.
Another version uses a 316 wet-pour 4x4 post holder. That's a post holder with two bolt holes on each side and tall sides. Then two rough-sawn 2-by lumber pieces will fit in the post holder. A floor joist and a stud can sit side by side or two studs can sit side-by-side.
The next point is that a ceiling joist can sit on one stud and bolt to the side of another stud. So go back to the foundation point and use two studs at each stud location. Furthermore, a floor joist can easily be set at heights by setting the floor joist on one cut-to-height stud and bolting to the side of another stud. The stud bolted-to can be carried to full stud height while the stud between floor-joist and ceiling joist must be pieced-in and bolted in place. Now these constructions require a bolted blocking using brackets, between stud locations, and up near the ceiling joist.
If the roof rafters are not a part of the ceiling joist in a truss design, then the roof rafters bolt to the sides of the extra-tall studs and sit on a fitted piece between the ceiling joist and rafter.
The whole house bolts together.
Finally, only use 18-8 nuts, bolts, and washers with 304L or with 316L. Otherwise, galvanized, but not zinc-plated, is okay for bolting two lumber pieces together.