Unless there's a specific statue in the law, wouldn't the landlord's duty to mitigate damages and the prohibition against double-dipping trump any such early termination fees?

Financing for your IRA must be non recourse, a conventional loan is recourse and as such your IRA would be materially benefiting (read prohibited transaction) from your personal guarantee (assuming you somehow could get a lender to agree to this, though that would be highly doubtful).

There is an ethical code for attorney's that prohibits direct contact with represented parties without the permission of their attorney.

There is a company called Lasaii who will structure your inherited IRA to purchase real estate so that you have the flexibility to use it as you want - no prohibited transactions and offset tax liabilities!  

EG HVAC seem ok in one case and prohibited in another.

They are not the same thing and in some jurisdictions it is prohibited, and considered a violation of Fair Housing, to deny based on ARREST record.

That's going to be an expensive reno, and probably cost prohibitive if the house is built on a slab.

@Zac BoyerFollowing are the similarities and differences between the solo 401k and the self-directed IRA.The Self-Directed IRA and Solo 401k SimilaritiesBoth were created by congress for individuals to save for retirement;Both may be invested in alternative investments such as real estate, precious metals tax liens, promissory notes, private company shares, and stocks and mutual funds, to name a few;Both allow for Roth contributions;Both are subject to prohibited transaction rules;Both are subject to federal taxes at time of distribution;Both allow for checkbook control for placing alternative investments;Both may be invested in annuities;Both are protected from creditors;Both allow for nondeductible contributions;Both are prohibited from investing in assets listed under I.R.C. 408(m).The Self-Directed IRA and Solo 401k DifferencesIn order to open a solo 401k, self-employment, whether on a part-time or full-time basis, is required;To open a self-directed IRA, self-employment income is not required;In order to gain IRA checkbook control over the self-directed IRA funds, a limited liability company  (IRA LLC) must be utilized;The solo 401k allows for checkbook control from the onset;The solo 401k allows for personal loan known as a solo 401k loan;It is prohibited to borrow from your IRA;The Solo 401k may be invested in life insurance;The self-directed IRA may not be invested in life insurance;The solo 401k allow for high contribution amounts (for 2016, the solo 401k contribution limit is $53,000, whereas the self-directed IRA contribution limit is $5,500);The solo 401k business owner can serve as trustee of the solo 401k;The self-directed IRA participant/owner may not serve as trustee or custodian of her IRA; instead, a trust company or bank institution is required;When distributions commence from the solo 401k a mandatory 20% of federal taxes must be withheld from each distribution and submitted electronically to the IRS by the 15th of the month following the date of each distribution;Rollovers and/or transfers from IRAs or qualified plans (e.g., former employer 401k) to a solo 401k are not reported on Form 5498, but rather on Form 5500-EZ, but only if the air market value of the solo 401k exceeds $250K as of the end of the plan year (generally 12/31);When funds are rolled over or transferred from an IRA or 401k to a self-directed IRA, the amount deposited into the self-directed IRA is reported on Form 5498 by the receiving self-directed IRA custodian by May of the year following the rollover/transfer.Rollovers (provided the 60 day rollover window is satisfied) from an IRA to a Solo 401k or self-directed IRA are reported on lines 15a and 15b of Form 1040;Pre-tax IRA contributions on reported on line 32 of Form 1040;Pre-tax solo 401k contributions are reported on line 28 of Form 1040;Roth solo 401k funds are subject to RMDs;A Roth 401k may be transferred to a Roth IRA (Note that from a planning perspective, it may be advantageous to transfer Roth Solo 401k funds to a Roth IRA before turning age 70 ½ in order to escape the Roth RMD requirement applicable to Roth 401k contributions including Roth Solo 401k contributions and earnings.)

I always distinguish between a city that actively allows Airbnb investment properties and a city that allows them only through a lack of prohibition.

One suggestion was that the soil will have to be sifted (that sounds like a crazy amount of work), another was to have the soil turned over and another was to get new soil (this would be a prohibitive amount of soil.