Here are the options that I have been thinking about:1.

Several options you can explore to get the down payment capital: Solo401k; HELOC on personal residence or from equity of the SFR; Cash Value Life Insurance Policy; Business Credit; Private Lenders, to name a few.

You should have some options! 

I havent gotten an insurance for this and a week after close I consulted some insurance provider and he didnt offer me insurance options.

If you want help structuring a scope of work or exploring different financing options, feel free to reach out—happy to offer insights!

I suggest your next lease have such a clause and that you make sure you can find the lease (but i have also somehow lost a lease recently).For where you are now, without a signed copy of lease i believe your options are limited.  

Staging your house well can help you attract more attention from buyers, which ultimately helps it sell faster and maybe for a higher price than an unstaged home (see visual):What Are My Staging Options?

If you use the Heloc option and decide to rent it out, don't forget that property (or you) will have to cover both your primary and secondary position notes.I don't personally see Marin being a great mid term market.

Be sure to understand the financing options out there for mobile home buyers and if you opt to carry the contracts on the homes you sell you should do some research on Dodd-Frank regulations. 

Yes, but the 3rd option is I pay the remaining seller note principle in cash via my own savings/lines of credit.