Cydny Jenkins

Okay,
Spent some time talking to Michael and he says he can build to support whatever we need to.
He's actually getting excited as everything is not new, he has straight walls, familiar corners and a normal roof. He says he was just overwhelmed with everything being different.
Is there a wall thickness that is optimal for thermal mass. Say with earth is 8" or 12" or 24" the best thickness for thermal mass. Michael says he can probably put 6-8" inside with serious support underneath or more outside. He would probably remove the metal so we would have roof, floor and studs to work with.
What would be the best material for thermal mass?

This sounds stupid but are rice hulls and strawbale insulation or thermal mass?

We are a couple hours east of Dallas and an hour plus from OK, AR & LA borders in rural Marion County which as I mentioned has no building codes.
Too far south for local strawbales and north for rice hulls but I make jewelry for Renaissance fairs and visit Kansas in April and Houston in Dec. so I could probably get a trailer and haul stuff.
Remodeling the single wide is a great idea since work has to be done anyway. It is an empty box with 1/2 good floors and walls the other just studs for walls and you have to walk on joists. It came with enough plywood and 2X4s to fix the bad floors. We had planned on fixing it conventionally while studying natural building--keeping an eye on everything we built ie. cabinets counters to be moved into new house and leaving mobile home as workshop. But instead of making up little projects to practice different modalities of building we could practice on the mobile.
We were planning on a summer kitchen/ porch for the north side.
It faces SSE. Is there a way to get thermal mass around it so it maintains a even temp?
We are going to take all the walls down to studs to make sure nothing evil is hiding there. If we have wrapped the mobile in thermal mass should we put in insulation.
Is natural plaster too heavy for plywood floors?
It's in the lowest part of the lot so I guess I'd have to do something about drainage.
A lot to think about.
Thanks Chris.

Chris,
Are you talking to my husband behind my back?
I can almost hear your words mumbled under his breath when I show him pictures of cob and eb houses.
You did make some great points. We are doing the project alone and though I hate to admit it age is a factor.

Forgot to mention--very low income.
Wood is so expensive, we're trying to use as much readily available materials as possible.
We have the clay, sand and a lot of rocks-iron ore I think- on site. And best of all no building code.

We are living in N E Texas on a small lot ~ .2 acres. We are in climate Zone 3 with 1" snow and 46"(in bucketfulls) rain. The avg. summer temp is 95 and winter 35 with a few days over 100 and a few days in 20's. The lot has a slight slope 3-4 feet over 100'. We are living(camping) in a small 12 X 32 mobile home on the lot and plan on building something small in the spring and summer--our big dog is pushing for a doghouse--using the method we decide for our house to be started spring of 2016.
My husband was a master finish carpenter and journeyman framer in PNW before 15 back surgeries. He shakes his head at leaving his 90 degree sticks but is game for whatever. He has put me in charge of deciding shape and composition of our house before he figures out how. I fell in love with earthships but we're in our early 60's and tire pounding and his back didn't seem a match. I love cob as well and he says he can stomp cob with a walker but earthbag seems to be a lot less demanding. I've seen a thread that said strawbales should somehow be incorporated with the cob or earthbags in Eastern Texas.
We're thinking roundish of 20 to 25 feet with straight walls open rooms with loft bedroom. Toying with a chickenwire, rebar concrete ceiling.
Can you start with earthbags the first 3-4 feet and finish with cob to the top of walls?
Any ideas or advice?
Thanks
Cydny