Come retirement, would you prefer the cash flow from 3 free and clear properties, or 15?

Talk to a good real estate attorney in your area, preferably a real estate attorney who has also handled at least some litigation.  

I am looking to buy another property by the end of 2017. something that is 100% financing is my preference.  

Preferably to purchase with Terms.

My father in law is nearing retirement age and prefers to buy rentals with cash because he would rather have fewer properties to think about even though he is only getting 5-8% returns on his cash.

Do you have any preference to large or small custodian companies?

I'm like 90% purchase business and generally prefer it that way (buyers are more motivated borrowers than refinancers, so I don't have to chase them around for paperwork), but when one like this that sells itself no matter how you cut it (did you notice I bumped your rate like half a percentage point and could still sell it to you?

good enough for FHA, but not good enough for conventional loans that require a 700+ score.Myself and my family are experienced DIYers and prefer to do as much as possible ourselves.  

I'd really prefer multi.

That gives you preference for the deal.