Boy-oh-boy! Does this all sound familiar to me? You bet! I see this question and pattern repeated over and over when people buy and move to the country.
Way back in 1999/2000, I was going through the same kind of scenario. Having just closed a run-down mobile home park I inherited, I was so turned off by mobile homes that I think I would have lived in a cave before buying one. If I had it to do all over today, I would go the small mobile home route for sure, or maybe build a permanent metal building with living quarters inside. The quickest and easiest way is to put a nice 40' travel trailer on the property and concentrate your efforts on building a permanent utility building and planning your home instead of spending all your time and energy on a temporary self-built structure. That's what I'd say to do in hindsight. It's not what I did. I'll try to be brief, but explain what I did and how much work it was. I've attached photos to illustrate.
I decided to buy a 24' x 24' portable building and finish it out as a cabin. I found a fellow near Fort Worth who built and sold several sizes and styles of buildings. He primarily sold kits to people to build their own, but he had a few buildings he had built and the 24' x 24' was for sale for $5k. The windows and doors were installed as was electrical and insulation. The building was actually two 12' x 24' sections (a double-wide portable building) with each section built onto skids. The fellow said he had a trailer for hauling the sections and would loan that to me for free if I bought his building. He would prepare the sections and load them out for me. All I would have to do is haul them to my place, unload them, and set them up. I had a relatively new 3/4 ton Dodge, so that seemed like a good plan. I got a hauling permit from the state and started early one Saturday morning at 7 AM. Because the sections were so wide and lightweight, I could not drive over 45 mph without the trailer setting up a fishtail motion. That's probably good, because I'm not sure the structure would have withstood faster speeds. However, at that speed, I was able to make two trips in one day, unload, and return the fellows trailer to him by 9:30 PM. WHEW! What a chore. I had hauled two big sections over 90 miles one-way to my property and unloaded them side-by-side without doing any damage.
I don't have any digital photos of the process, but I laid 2x6s down flat on the ground at 90 degrees to the skids so I could push the sections together using my tractor. It worked very well. Also, the flooring was screwed down, so I popped that up and easily tied the two sections together as I leveled the structure. Then, for the next 6 months I spent almost every spare moment finishing out my apartment inside the building. Because the walls were already insulated and were 2x4 framing, I didn't want to weaken the structure and just added the plumbing on the outside. I could have hidden it better, but that wasn't a priority, and I wanted to make it easy to cut when I moved the cabin later. The first 3 pictures below are my cabin and wellhouse that I built to match the cabin's style and color. In the picture of the back of the cabin, you can see the outside drain pipes and the skids are clearly visible under each half-section.
I wanted to keep a storage area because the cabin had a very nice garage door, so I built my living area in the front and a laundry room and bath in the back of the storage area while leaving a 12' x 16' storage. If I didn't need that storage, I could have used the extra room for a nice bedroom, but instead I put a futon in the living area and also a single bed. The finished inside pictures show how well things turned out.
Finally, fast forward to the present and my cabin is still exactly where I put it over 11 years ago.

Hundreds of times I have said I was going to move it, but it just hasn't happened yet. You can see the cabin in the final picture. I've used it a couple of times as guest quarters, but still I would prefer to have it moved and use that area for a nice flower garden. Oh well. . . it will happen some day.
If I had it to do all over again, I'd sure go the travel trailer/mobile home route and make my life much easier. It's just that at the time this seemed like the best approach. It worked well, but it was a lot of work.