@Michael LeeBoth a SD IRA and a Solo 401k can receive transfers from your wife's existing IRA and then be able to invest into a huge array of assets including both traditional (stocks, bonds, mutual funds) and alternative (real estate, precious metals, private companies, tax liens, etc) assets.There are several differences between the 2 retirement structures, however.

I understand the irritation but I would focus your precious time/energy elsewhere.

That 30-year fixed financing is precious.2) Could you sell the house and buy a small multi-family (2-4 units)?

But they get precious little sun in the winter, which lasts about 6-7 months.

Investing in dividend stocks can be a great way to generate passive income. ...Real Estate. ...Precious Metals. ...Invest in Yourself.

On top of all that they're less stressful to own and take up less of my precious time. 

So if you become the owner you own the liens also.If grass is high and no one is cutting it you may get more before you own property.Can you contact precious owner and see if they will go ahead and feed it over to you?

Wholesalers telling sellers they have CASH BUYERS-INVESTORS and not closing if their so called "cash investor" does not buy, wasting 3+ precious months of summer marketing time.Now don't get me wrong, Agents that take a listing (buying a listing) and not being straight with the owner about pricing the property as per SOLD COMPS are hurting sellers too. 

However, if you let the call go unanswered, you have just wasted your precious marketing dollars!

@Jesse KindraThe following IRS website is a good resource for self-employment requirements. https://www.irs.gov/businesses/small-businesses-self-employed/self-employed-individuals-tax-centerFollowing are the similarities and differences between the solo 401k and the self-directed IRA.The Self-Directed IRA and Solo 401k Similarities Both 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); and 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 2015; 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.)