While I wouldn't need to make a too much to supplement my retirement income, I definitely like the process of REI, and would like to explore some additional avenues like getting my RE license or possibly look at doing financing.  

You will need a longer history of earning those variable income types if using a degree to supplement your work history.As mentioned above, if you truly want to buy an investment and you won't be living in the home,  investment properties don't qualify for FHA loans.

We BRRRR 8-10 peryear and the flips supplement and money left in the BRRRRs.How do we choosewhich ones to BRRRR?

Building a note investment business that generates monthly cash flow of at least $1K a month within the next 5 years to supplement my expected other sources retirement income is my current goal. 

I don't see too much of an issue of negative cashflow when it comes to a house hack if your intention from the start is to treat a similar property as your residence along with your abilities to afford the expenses without any rental income as a supplement.

Looking to buy a cheap property to start my path to financial freedom via supplemental income.

We supplement during the colder months with heavy blankets that are kept separate from the bedding.

Not really a big business, but a good supplemental side line at home.You will have issues and upkeep with your dump station.

If not then as a landlord you are supplementing your tenants rent payments.

Also how 'easy' is to get a non-recourse loan to supplement the 401k funds to purchase a property?