I have never done one but my dad just finished one and the rules about which you select as possibilities vs what you actually purchase are strict and a little bit prohibitive. 

Some say it’s helping , some say it’s promoting your business which is prohibited..Potato / PotatoIf you look hard enough, you can find me ..Thanks Vernon  

Because of the potential for UBIT and prohibited transactions depending on the specifics of the flipping activity, rentals are generally more appropriate for Solo 401k funds.

They can prohibit STRs. 

They actively prohibit you from having access to the property until close once you have but money down and are under contract.

I'm thinking about not starting out in NYC just due to the prohibitive prices so I'm exploring Tennessee, Indiana, and Arizona as good out-of-state locations to start with more affordable properties (but would love to hear other people's perspective on this).

This is how some jurisdictions are prohibiting a STR in residential district because are using the hotel/motel which is a commercial use.

The only way that this would be possible is if the transaction was not listed on the MLS which in most cases would require a client signed waiver (since the MLS wants to have all possible listings, it typically prohibits agents from listing off MLS unless there is a waiver signed by the client).Listen, I'm not saying that banks care about MLS rules or that ultimately they dont get their way 99% of the time, but I am saying that you are 100% wrong in your assertion that the rules don't apply to banks.

I especially valued hearing how he author has worked through logistical complications that were once super prohibitive for out of state investing (in, paying contractors and ensuring sound work is done).Thanks for this helpful tool!

I doubt you would be able to use the same closing attorney if the lender's closing instructions prohibit second position liens.