Well said, echoing what most of the rest of us have said.Interesting thread. I scrolled through the replies to see whether anyone has done this. Finding none, I'll add my two cents. I have actually done this! Twice! From the CFI perspective.
Briefly, I'm a 12,000-hour ATP, ex-USAF T-37 IP. I built an RV-4, flying for 24 years now, and I'm nearing completion on my RV-10 project. I maintain my CFI mostly for the fun of it. I mostly do RV transition training, tailwheel endorsements, aerobatic instruction, formation instruction. Mostly for fun.
I have taught two new students to fly in their own RVs. One guy purchased my neighbor's RV-10 without a pilot's license, the other was my neighbor lady who built an RV-12 as a post-solo student pilot, most of her training in a C-150, but obtained her Light Sport license in her new RV-12.
The RV-10 guy bought the airplane without a pilot's license. He had bought it from my neighbor who has built a bunch of all models of the RVs. I happened to be down there at my neighbor's house, shooting the breeze, when I overheard the purchaser complaining that he could not find a CFI that his insurance company would insure for his initial training. I offered to do it, and sent him my numbers, which his insurance company agreed would be fine.
And that really will be your difficulty: the insurance. You don't have to insure the airplane, of course. But most people having spent that much time and money building the airplane will want to insure it against loss and liability. That will be expensive! Have no illusions on that point. Having no time in type, experimental airplane, and no flight experience and no license, insuring it for giving instruction: that will be expensive and difficult to find! Your insurance company will insist that the CFI have experience in make and model. That will be hard to find.
If you can find a CFI and insurance, yes, it can be done just fine. The RVs are very honest airplanes and I enjoy instructing in them. The complex RV-10 will take more time for you to learn in. Plus you have to demonstrate knowledge of the avionics and systems on your checkride. Having more complex avionics and systems in the RV-10, you will be tested on those. But the mechanics of learning to fly in the RV-10 are no more difficult than other airplanes.
You will also, however, put more wear and tear on your airplane learning primary instruction in it. You will bounce landings and impose side loads learning crosswind techniques. I personally bought a Cessna 140 to give primary instruction to my children, just to keep the wear and tear off of my beloved RV-4!
In conclusion:
Yes, it can be done just fine. Insurance and CFI experience will be the sticking points. You will put much more wear on the airplane than if you learn first in a cheaper trainer. Were I doing it, I would get the license in a simple and inexpensive trainer first, then transition into the RV-10 that you built with some flight experience already under your belt. But you are the one paying the bills, so you make the choice yourself. There is no wrong answer either way. Don't be afraid to learn in your own airplane. Just know the tradeoffs.
To add one other thing, not only will finding an instructor be challenging but finding a DPE that will do the checkride in an experimental aircraft will likely be most challenging.