So even if you currently manage 100 properties, if none of them are 5+ units and you, or an entity you are a member of, are not on title, then you have no experience.  

An LLC is a passthrough entity for tax purposes unless you make a C corp election. 

I make sure (1) the borrower has a 10-20% (or more) down payment of his OWN capital invested (2) I understand time value of money and use a realistic and appropriate interest rate to determine the actual value of the note I’m holding and (3) obtain a personal guarantee unless the entity purchasing the property has financial strength in its own right (4) the lien I hold is in 1st position.

got it, but the business entity in question wether LLC, corp, or whatever the case... does it need to be 100% owned by my wife since she can position herself as "full time" investor as I'm a full time W2 employee currently. 

Fairmount is a newer entity which is a little concerning.

A reverse exchange is where the intermediary creates an entity to take title of  your replacement property before you close on your relinquished property.

Is the duplex owned by an entity or partnership of individuals or...?

You are closing these loans in an LLC or other entity.

Someone told me if I put the property in an entity's name, I could sell the entity with assets and the deed would not need to change.  

Same goes for DSCR loans - even if theyre not on your credit report, if you PG'd the loan (which is almost always the case), it will be included unless there is a justification to exclude it (such as it's been paid by your entity for at least 12 months and is included in a business cashflow analysis).If you're finding good deals and have cash for downpayments, but are hitting DTI roadblocks to acquire more properties, then DSCR loans are likely the answer.