@Zane AbnerFollowing 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); andThe 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 used;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.)

Finally, NY State passed a law that prohibits second had car dealers from leasing second hand cars which is 50% of his business, and he was forced to close.

However, some state and local Fair Housing laws, such as Chicago's Fair Housing Ordinance, do prohibit discrimination based on source of income.If your city or state prohibits this type of discrimination, you cannot reject all Section 8 applicants outright.If you have multiple applicants, or are waiting for additional applicants, you are well within your right to not respond to anyone until all applicants have been submitted, and you have chosen the applicant that is most qualified, because there is no law that say you must call, or otherwise, anyone back, ever.  

Most leases will prohibit subleasing because of the extra wear and tear from STRs.

Quote from @Kevin Sobilo:  My leases state that any monies owed are payable "as rent" so that if they do not pay that damage bill I can simply choose to evict them for "unpaid rent" which is simple and cookie cutter.FYI this is not legal in Colorado. https://leg.colorado.gov/bills/hb23-1095 prohibits "A provision that characterizes any amount or fee set forth in the rental agreement, with the sole exception of the set monthly payment for occupancy of the premises, as "rent" for which all remedies to collect rent, including eviction, are available"As for the $600 faucet... it sounds like you just called up a random plumber and told them to install a faucet.

But my understanding of workman's comp is, the worker can only sue the workman's comp carrier, he can't sue the business owner as is the case in other lawsuits, since state workman's comp law prohibits it.

Now if I wanted to move my driveway and add another story on to my house, I'm sure they'd get involved.You'll need to check the HOA bylaws and amendments to see if they have a cap on rentals or prohibit Airbnb.

You are correct, Boston's property values are going to prohibit cash flow.

It looks like the cost of insurance can be prohibitive and it seems like there is opportunity for not only cash flow but appreciation.  

The following covers the differences and similarities between a solo 401k and an 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; andBoth are prohibited from investing in assets listed under I.R.C. 408(m).