@Richard McLain, Thanks Richard. You are not the first to consider the way I would do some projects to be insane. Check out my Blog. https://www.biggerpockets.com/member-blogs/12388-abandoned-property-adventure-on-wildside
In defense of my idea, many jurisdictions such as where I live, Thurston Co. WA, do not require a contractor's license for a homeowner to build their own home, garage or ADU. Here, homeowners who pay for a construction permit, may construct their own foundation, framing, roofing, wiring, plumbing, mechanical, etc. Homeowners are also permitted to hire "help".
In the scenario I suggested Jillian would need to act as the builder, and the person she contracts would be her help. There is nothing that prohibits the helper from being more proficient at every aspect of a project than the owner builder. If it were my project, I would look for a helper who is has some experience in every aspect of home building. If the contractor is weak in one area, a local Subcontractor can readily be brought in on a limited basis to offer supervision/management. But generally there should not need to be any subcontractors, and thus no subcontracting delays.
There are a surprising number of generalist type builder's all across the US who do have broad experience in home building. Our nation is blessed with people who have built either multiple homes from scratch or just their own home. I am one of them. It is true, that a generalist, will not be as fast at any craft as are the specialists, but he also won't have any of the delays typical caused by waiting for a subcontractor to come perform their specialty.
Here in Western WA, a proficient professional contractor, will complete the construction of a house, from foundation pour to final County inspection in 4 months. They do it all the time. Not sure why allowing 6 months for a smaller project, would be unrealistic?
So when the budget is tight, one option toward getting it built is for the owner to step up and do more of the job. Doing more of the job can include taking on the project as an owner builder, handling the permitting, looking outside of the local market for cheaper help that is proficient in building, sourcing all the required materials, and supporting yourself and your generally proficient helper with locally licensed supervision where needed. All that is a lot of work. It is certainly true that many people who have built their own home, do look back on the project and consider it insane.
Still, if it is important to get a project built within a limited budget increasing owner participation is one way.
There is always a way. There is always another way. And there is always a better way. Your observation about the insanity of this way, is worthy of consideration.