I don’t think you would be able to include the mobile home in any structural load bearing way. It would just save you money on interior walls and infrastructure.
As far as wood goes for making a berm shed to put the trailer inside you’ll have to scrounge. In my area there are lots of pine trees. The trees are planted very thickly, then someone buys a property and decides they want to put a house on it, so they “park” it out, thinning out the small 3” diameter trees for fire prevention and to make it so you can look through the forest. Many people in my area will cut these trees for people and then haul them to a fence post mill to be made into fence post. There is even a government program that will pay the tree cutter to do this. Those trees would be the perfect size to use for roofing a berm shed.
For larger logs, perhaps talk to tree trimmers and see if you could haul off trees they cut down, just tell them what diameter and length you want and you’ll have to be quick about getting out to them. This will require a flatbed trailer or a very heavy duty rack on a pickup. A lot of tree trimmers have skid steers they can use to load you.
Also, developers clear house lots or commercial building lots. They will pile up the logs to burn and they are often free for the asking.
Another source is right of way crews that maintain power line right of ways.
Right after storms there are often many trees blown down that are free for the taking. In our area there are state and national forest. If the tree is on state or federal land and it blows down into the road right of way, it’s fair game. Saves the state the money of dealing with it.
Another source is pallet materials. Some areas have companies that produce a ton of pallets and crates. Some crates use 10-12’ long 4x4’s. This could be repurposed into decking for a roof. A pallet breaker tool can be purchased at Home Depot or online for taking the slats off efficiently, and an air denail gun will make quick work of removing the nails from the slats so they can be reused.
Another great source for wood is tearing down houses or barns. Be careful here though, it’s easy to get in over your head! It is a LOT of work! However, if you have the time you can do a little every day after work for a few months and you’ll have a pile of lumber that is well cured. Old homes often have rough cut lumber, and some have 1x12 decking on the roof that would work very well for decking your roof and sides. I helped tear down an old Victorian home one time that had really nice lumber in it. An uncle did this as well, tearing down several houses, and built three houses for himself and his two sons.
With resourcefulness you will be able to come up with the materials. Make sure to protect the materials well, put pallets on the ground to stack the lumber flat in so it’s protected from ground moisture and doesn’t warp. Billboard tarps can be purchased for about $50 online and make excellent heavy duty tarps to protect everything with. If you know someone at an outdoor advertising company you might even get them for free, but if you do don’t let anyone know about it! Your source will be dried up in no time.