I was also looking at selecting something different (not rentals) to invest my retirement account into besides stocks, bonds, and mutual funds.

The process just involves reaching out and confirming intent, draft a mutual termination, payment of consideration (if any), then signing everything, vacate, handle deposit, etc.

Overall, I think living across the street can be beneficial since you are just getting started, but it really comes down to personal preference. 

Also beneficial for those who invest with retirement accounts which have a harder time qualifying for financing.- Massively scaleable deal flow: Let's say you vet 15 syndicators and get on their investor lists.

Has anyone done some creative financing that mutually benefits both parent and child?  

I hear your point that staying specific can be beneficial and finding your niche is better than venturing outside of it and increasing risk.

When I talk to tenants on a cash-4-keys situation I let them know that if we can not come to mutually agreed terms voluntarily we will be left with the only remaining actions available of civil suite, judgement and wage garnishment which will impact their ability to lease a future place most likely, their credit rating, and any future loans/ lending attempts.

This can be in a Roth IRA account, invested in things like mutual funds that can be liquidated easily. 

I know they can be beneficial for certain things.

Biggest threat is the eviction moratorium here.2) You can go online and sell all your mutual funds in 30 seconds on Fidelity or Vanguard.