Guessing from your question, you probably have no concept of what life is like without unlimited fresh water & electricity and ability to instantly dispose of waste water (sewage). None of those things are magical in an RV and the onboard supplies are extremely limited, even in a very large RV (30-40 feet). If you don't adopt a very conservative lifestyle, you probably won't last more than 1-2 days without running out of one or all of those things. In any case, you will be frequently hauling fresh water to the RV and waste water to a sewer somewhere, and finding some method of charging batteries daily. And still no electric heat or a/c to use.
As a practical matter, you need to get temporary electrical service to the new home site (the builders will need that too), a fresh water source (well, city, or a service that delivers to a large tank onsite), and a septic system. If possible, make those the base of whatever utilities the house will eventually have, but temporary is ok too.