Take pictures of contractor's trucks you see driving around.

even shipping costs from so cal to nor cal throw most scenarios for modular homes out the window. perhaps based on your experience you can minimize those drastically. 8k a truck load. 3 trips minimum. 

Save every penny you make, live with room mates, drive a beat up truck, house hack distressed properties and spend all of your spare time DIY rehabbing them.

Trucking seems to be sliding into recession, and downtown Office CRE has been in recession for 2 years?

Truck parking lot development I have high interest in if you come to columbus. similar to mobile homes but you don't need infrastructure and you aren't dealing with housing.

You'll see a lot of vans & trucks with no business names on them - these are the guys to approach as they're hard working and not spending money (yours) on advertising.Be prepared, most won't have business cards and may not be friendly.Persist and you will start to build your crew.

My work around was to find a 75 year old dude with no credit and no assets, who wanted a new truck.

Let's say $100/hour fully loaded, plus a truck, overhead and then add another 20% profit on the total (material and labor), because that's the whole point of running a business.

My wife used it to write an add for one of my Tesla's I am selling ( new truck is here ) and it writes a decent add I have to say. 

In Reno, NV the Tesla factory and building of the Tesla Semi-truck factory has been bringing more, construction, executives and engineers to the area for 1-8 weeks.