Projected expenses won't be enough.

I wish you well in your project. 

The guest house has STR rental history but the other two units would need to be based on projections. 

How would you manage risk? 

Not impressed with other large institutional managers who are very light with boots on the ground and in many ways have the attidude they are assisting you in managing the property, not managing it for you.

Here’s a breakdown of some of the information you may need to provide for a cost segregation study.For existing buildings:List of equipment on the propertyProperty settlement stateAny appraisals or purchase/lease agreements Property maps or blueprintsSchedules, change orders or documents for future renovation plansSupporting documents for calculating real property book valuePrevious purchase price allocations that separated assets into their appropriate allocation and valuePast site inspections and photographsDocumentation that proves or records deterioration of assetsFor new construction:Contracts or contract paymentsLand and property sizeBlueprints of projectList of equipment involved or purchasedList of projected costs including costs for land developmentApplicable site inspectionsConstruction schedules and payment requestsPhotographs of completed assets or work in progressCost segregation specialists typically have an organized plan for the collection and analysis of the information provided.

Again, if your $250k is true, and includes all the electrical upgrades, new plumbing runs, potentially new foundation pour (since I assume the existing garage slab is not capable of supporting a new two story house), I am guessing since I don't know the market, but assume you will have a lot of equity by completing the project.

Here are a few high level thoughts for you as a beginner:-Don't lend in second position-Don't do deals with new investors-Don't experiment with new strategies, even with experiences investors- ie, don't jump in to a first development project with someone just because they've flipped 20 houses. 

Plus  2 years free property management.

For your GA LLC, filing correctly is crucial since you're based in CA and may need to handle multi-state tax filings.A real estate tax accountant can guide you on deducting renovation costs (likely capitalized rather than expensed for a flip), managing depreciation for investment properties, and tracking expenses related to your flip.