I will be using the extra equity to add value to the park with more pads and electric hookups.

It’s going to be very hard to find a good contractor who will actually build on time and on budget for any new build now and many don’t want to jump through extra draw hoops such as VA.Not trying to discourage you because anything is possible, but it may serve you well to learn the ropes first on an existing building…

A company might add a "commission" on top of the agreed upon price; plus they tack on extra closing costs that you are not aware of until you see the HUD1 at closing (like a double title policy charge). 

It will continue on without extra fees or penalties without any further contributions besides organic gains and dividends.

You should specify the allocation of depreciation, income, responsibility for extra capital expenses, etc in an operating agreement or JV agreement. 

It wouldn't be fair to charge Tenant A extra to cover losses caused by Tenant B.

Like I said I would need approximately $40-50k in extra funds to complete it.

Additionally, it has a boat lift on a river that leads to the ocean, a 3 car garage, and extra land with RV connections already in place.

To estimate appreciation, I currently use the general inflation benchmark as a baseline, with a few extra point for the Bay Area.As far as the exact appreciation percentage per year, that is not something we can control or accurately predict.My gut feeling is that higher inflation will translate into higher appreciation.

Taxes are mostly pass through so your added expense is mostly LLC filing fees and extra tax preparation expense for all the entities.