You may wish to confirm that the new 401k provider has experience with the particular investments in which you intend to invest your retirement funds as you very likely will have questions in terms of the mechanics (e.g. how do you invest in real estate, etc.).3.

The only thing I can think of is mechanical liens from the rehab - but can’t be too much... 

In my area some of them even do specialized investment inspections that look specifically at roof, wiring, mechanicals and foundation.

My question is how soon/what is the mechanism for selling equity in the 15-unit after I close. 

I am 100% owner on everything and am using the single tax payer exclusion to pull of the 1031.My question is how soon/what is the mechanism for selling equity in the 15-unit after I close.

That is a reason to be weary of putting too much emphasis on cash on cash returns. 

If you want to get ahead, make sure all doors are unlocked, all mechanical systems are started up, and note the location of the water meter/shutoff.

I agreed to a few items for them (added insulation in a wall, added a drop ceiling in a mechanical space, and the biggest was making a half bath into a full bath).

If you delead, and maintain the standard, you will be in the clear.Here's the law (emphasis added by me):460.100: Duty of Owner(s) of Residential Premises (B) Whenever any residential premises containing dangerous levels of lead in paint, plaster or other accessible structural material undergoes a change of ownership and as a result a child younger than six years old will become or will continue to be a resident therein, the new owner shall have 90 days after becoming the owner to obtain a Letter of Full Compliance or a Letter of Interim Control, except that if a child younger than six years old who is lead poisoned resides therein, the owner shall not be eligible for interim control, unless the Director grants a waiver pursuant to 105 CMR 460.100(A)(3).

I would like to emphasis the finance part that @Benjamin Seibert mentioned.