I definitely want to create a for-profit entity that has a giving component, similar to TOMS.

If you want some sort of rental component to your primary residence, you can always house hack with a rent-by-the-room model or find a place with a basement apartment or carriage house out back. 

However in law, record keeping is a major component in winning a lawsuit, which is the reason for even doing an LLC of any kind.

@Raj Janakarajan as others have said, a 5th unit will likely be detrimental to your long-term value.

Any inputs from 90 days ago are only just starting to show up in market statistics, and all of the components are there to suggest we'll see stagnant, or even softening, prices in the next 6-18 months, in some markets. 

Right now I am looking into a structure like this:-Borrow from an individual with an IRA -> convert to a SDIRA-Make loan interest and principle payable at the end of term (because it's an IRA)-Structure similar to a construction loan with monthly drawdowns of about $5k for the highest probability of success with direct mail-Possibility for an equity component: pledge a percentage of profit along with normal interest in the promissory note (a joint venture)Would this be attractive to a potential investor considering I am wholesaling in California and the average fee is $15k-$20k on the lower end?

@Ry Eikleberry, The most critical component of success in any venture (and real estate is no exception) is your ability to draw a team around you. 

After cutting them a check for $10k then I got my CPA involved as they needed to confirm the tax components of the fund. 3.

We were primarily interested in finding a mobile home park that was priced at a 10% cap rate (on lot rent only), generated over 20% cash-on-cash returns, had good management in place, was in a good market, and had a light value-add component.

So often these for sale flyers have critical errors or omissions in them that affect the cash flow or lendability of the property.With my clients we have a confidentiality component in the LOI so we can get a look at the lease early before the purchase and sale stage.