An excellent resource for a prospective builder are the books suggested on this thread:
http://www.pprune.org/flight-testing...ew-thread.html
If, upon becoming well familiar with a lot of these themes, the designer/builder feels confident to go ahead, then they are doing it "with their eyes open".
I have known many amateur builders, and among them, two who designed and built their aircraft. I never flew in either, but spoke at length with both builders. One was agreed by all who commented to be a design disaster, and flew only the one time. The other appeared magnificent, and the several hundred hours flying on it suggested it was a very worthy design.
But a caution (with no disrespect to the OP): The decision forces which come together to result in an amateur built plane usually include a desire for cost reduction. This is false economy, even if your design/build time has very low money value to you. Certainly excellent amateur built aircraft result from a labour of love, but that is not cost reduction, and now your "love" is flying = greater risk to it. This links to the next well know risk...
Builders throw themselves headlong into building, and let fly skills lapse. There is a natural resistance to now want to spend money and time renting someone else's plane, when "soon" you'll have your own. Then you do, and the flying skills you may have had, and deteriorated.
For this reason, there are regulations about the piloting experience required for first flights on amateur built aircraft. But, as an experience flight tester of GA aircraft, I can assure that a PPL with a few hundred hours on a 172 or PA-28 is not ready to fly initial flight testing on an amateur built, much less one of unproven flying qualities.
Builders must adopt a very serious attitude toward this, knowing that their pride and joy should be test flown by a very experienced pilot, and that they will need recent experience on something similar before they launch off.
I am a personal witness to a fellow wrecking his newly built Kitfox right in front of me on my home runway. He did not hurt himself, but the plane took a three year rebuild following his blatant flying error. As I flew him home, I engaged him as to his flying experience: 250 hours in 150/172, spread over the preceding 10 years, with only the rental recency minimums on the past few years. (So he met the minimums to fly his initial Kitfox flights, and did). One hour in the Kitfox with his taildragger buddy for familiarization, and his crash hour was his 7th on the Kitfox. That was a very expensive flight! (it was not insured).
Bringing an amateur built to flight will encompass many more factors than appear at the outset. They can all be managed, and overcome, but it will not be a cost saving exercise!