So I can put my terms, such as a non refundable deposit, rights to the contract if assignee fails to perform on C.O.E, rights to communicate with escrow agent after assignment.Im not a realtor, new investor.Any escrow agents in SFV, California whom are familiar with assaignments

Some only accept accredited investors some also accept non-accredited but sophisticated investors for their deals.

I decided to include my Real Estate plan for public critique.

100% financing is tough...even for private lenders, unless there are compensating factors (great track record, proven successes, strong reserves, great credit score...maybe even good job/w2 income (usually not a factor for non-bank investment property lenders, but may be for a private individual)). 

He has PCS orders and they are moving out at end of July.Couple downstairs with dog is non-committal about their plans, have given no notice, but MIL guy has suggested they are looking for a place and may move before or by end of one-year lease in mid-September.MIL guy has explained that he and his wife live upstairs and maintain that and the front yard, and the other couple with the dog live downstairs and maintain that and the back yard.

Let's chat in private as I do not want to seem to solicit to anyone and everyone on a public forum but in general our innovate model that installs in applications where plumbing is not separated probably runs $200-300 per apartment unit ($400-600 for an entire duplex).

etc..You can try to go conventional, to a community bank/portfolio lender, or to a non-bank lender for the above. 

I don't know whether this is typical, but my experience is based on several years buying foreclosures, and my wife as a VP for a finance company with non performing loans, many of which were real estate.First, for the foreclosures I looked at, most if not all were at public auctions.

Most private lenders, hard money lenders, and non-bank lenders will want to be the first and only lien on the property, so it may not be possible to borrow $50K and put a second lien/further debt on it.Why wouldn't you just finance the whole thing with one lender? 

Relative would give you personal non-secured loan, you payoff the balance of the 401k loan, rollover funds into self-directed IRA and then IRA would buy a rental property.