Virtually no skill is required, as everything a builder needs to know to successfully complete an RV can be learned “on the job,” or by carefully studying the builders manual, or by seeking advice from other RV builders, either local or on-line.
One requirement that’s more important than skill is having the right frame of mind. Building an airplane requires dedication, commitment, a willingness to learn and the ability to make (and correct) the occasional mistake without throwing a frothing fit or suffering an ulcer. Experienced builders will often gently counsel people whose personalities demand absolute perfection and accuracy to seek another type of project.
RVs have been built by people of every imaginable background and skill level, and currently are being completed and flown at the rate of about one per day. It is a very “doable” thing.
More information and detail is available on the Building an RV page.