James,
Determining one's "residence" can fill a real thick lawbook. The best place to start is by asking the question, "residence for what purpose?"
For example - for the purpose of getting married? For the purpose of getting a divorce? For the purpose of paying income taxes? For the purpose of paying real estate taxes? For the purpose of avoiding paying taxes? For the purpose of obtaining a driver's license? For the purpose of whether or not the local LEO thinks you should have a driver's license from his state? For the purpose of licensing your automobile? For the purpose of temporary residence or permanent residence? For the purpose of gun control laws (added to perhaps get you on topic)? For the purpose of qualifying for in-state tuition? This list goes on and on.
When you caption your question "Dual residency?" you are making an assumption which may or may not be valid, once again depending upon the purpose for the question. Yours is less a question than it is an argument.
Seldom does one have a choice to simply declare his residence, or domicile, if more appropriate in a particular case, in one state or another. Both words are matters of legal status, and the law generally does that for you whether in accordance with your personal wishes or not.
Given the situation you describe yourself in, and your future intentions, many would probably say you remain a domiciliary of PRK for most if not all the above examples until you get your house in Nevada built and move into it permanently.
You may be confident, however, that Nevada, like most states, will be happy to take your money if you want to give it to them, for example, to register your automobile or to get a driver's license. If you expect those licenses to insulate you from PRK regulations, don't be surprised if a PRK LEO says, "Sorry, James, you are a resident of this state, you have to meet our requirements. Both your Nevada automobile license plate and your Nevada driver's license are invalid here. Come along with me."
Will one sometimes get hung up between two states when his status is unclear? Of course. But I dont believe that is true in your case.
Jim