Whenever anyone invests outside of their "comfort zone", or their zip code, they really need to get a good handle on it.  

I suggest being more specific as to describing the purpose and scope of operations, saying to do all things customary and then doing what you think may be customary can venture off into other tax code classifications of business, such as lending, and doing too much of another activity may put you in a different light and acting outside the scope of the primary mission.  

As such, "combining" funds in the manner you suggest becomes very difficult and even if done "in the recommended fashion" not without risk.There is an interpretation that an IRA/401k and disqualified party may joint venture in a very rigid fashion.The title is vested jointly on day one, reflecting the percentage of ownership.The equity in the project may not be altered in any way between the JV partners.AND - the tricky part - this is only OK if both sides could do the transaction alone and are not being enabled to participate in a transaction they would not have been able to without access to the disqualified funds.So, if your 401k (could) purchase a property - perhaps with a non-recourse loan - and chooses to JV with you instead, that is OK.  

To become a member, you must pledge to a strict Code of Ethics and Standards of Practice. 7.

No pealing paint gfci per code windows no leaks in roof etc. 

Also, encumbrances that come from code violations, water/sewer bills, or any other special assessment will go along with the property and does not get wiped out from a tax foreclosure. 

Do I just choose random streets all over town, or search popular last names, or just choose a particular zip code and stay within it until I get a good amount?

Long story short, I have to do more construction and alterations int he form of sprinkler systems and fire alarms to make the property compliant.As difficult as this can be sometimes, I feel blessed to own my own triplex.

And while you cannot 1031 into your next primary residence immediately, there are provisions in the tax code to later convert a 1031 investment property into your new primary residence. 

The SIC code, the history of purchase etc.