Further, if you decide to sell that property and reinvest into another investment you don't have to do the 1031 exchange since you are doing so inside of a tax-sheltered vehicle (IRA). 

Is it more cost efficient to claim miles on your own vehicle or purchase one with your business and deduct that way?

This is not true and I will explain why.Can you provide a realistic annual maintenance cost that applies equally well to the two vehicles below:One is a new economy car and the other is a wrecked Humvee.

My biggest or most unusual problems were: abandoned vehicles, a person escaped from a mental institution, tenants with pet rattlesnakes that escaped their container, a round trip visit to the dentist for a wisdom tooth removal, a one way bus ticket from Kansas to Georgia, cashing $25,000 worth of checks each week for a group of guys from out of state, etc.  

Tell them when they ask that you do not release the reason for rejecting simply that they did not meet their screen criteria.Many times applicants are rejected due to appearance, attitude, upkeep of personal vehicle etc.

Each sale would be its own 1031 exchange but you can combine 1031s into fewer larger properties or passive vehicles as long as they fall within the necessary timelines. 

Use the remaining cash to purchase a passive investment 1031 compatible vehicle like a TIC or NNN lease and pay tax on the mortgage buy down. 

Then we setup other investment and savings vehicles like Roth IRAs and an HSA.  30% of our take home pay was being set aside.Then we read the @Scott Trench book Set For Life and a similar article he wrote (The Simple "Secret") about capital preservation, and it blew our minds. 

Which vehicle would be best to run my Real Estate investments within: LLC, Corp, sole pro ?

@Blake ChapmanMy personal favorite vehicle for leveraging a property is a Home Equity Line of Credit.