Regardless of which you choose, you'll also have to talk to the county inspector to make sure he's on board with your plans. You may go to his office and ask him for the plans of the structures that you mentioned and ask about completion times, which seems to be your biggest concern.
Any Building and safety that does this is in violation of copyright law....People, some, have to pay money for plans. Architects, builders, make thier money selling them not giving them away. It can take ALOT of time to develop them and they are not meant to be given away for free.
I fail to see how the rest of the house can be built for $10,000. Provide how much of that is going to windows and door schedules, HVAC, plumbing, electrical, etc...that is available for the envelope and we can go from there. Include in that cost a soil test without no advice can or should be given. We need to know what wind and seismic zone you are in as well or one could be putting their family in more harms way than living in a RV despite the high cost of HVAC. I'm pretty sure Ark is designing to 90 MPH wind in Seismic zone B but check. The state of Arkansas follows IBC 2006 (more applicable to commercial buildings) for homes old and out-dated, we need to know what building codes are being locally enforced at the building site if any. Just because a house exist or is grandfathered in does not mean it is currently allowed. IBC 2006 does not have a code path for strawbale or earthbag.
I know what it's like living in a RV, like to help out but need more info.