All new except for the refrigerator that they brought out from the back...never used just dented from stock.

Sure, stocks and bonds could generate higher returns cash on cash, but not in a mutual fund and not by an amateur just picking something off of e-trade.

I have a 401k invested in stock funds, and would like to avoid the ups and downs of the market.

Put another way, is this investment a replacement for long-term bonds, or a replacement for another investment (value-add real estate, stocks, etc.)?

A CPA can set it up pretty quick.Your payments received will be 2 components: interest, and principal.The interest is income, not cap gains.The principle received will be 2 components : return of basis, and cap gain.

I sold the property on contract for deed for $5K down and $550/month which includes PITI (Principle, Interest, Taxes and Insurance) for $24,500 at 6% interest.It's not a huge return, but the deal was done with no money out of pocket and now I'm cash flowing about $300/mo and I basically got paid $5K to  buy this house.The original seller was happy because she was able to get rid of a house that was costing her money every month because it was vacant, and she was able to help out a young man (me 😁) that was trying to do something positive. 

Use the cash stock as the revolving rehab fund.

Hello @Wayne Brooks, thank you very much for your comment.You bring an excellent point, which has made me doubt investing in Tax Liens in FL, unless it is seen just as an alternative to CDs, Stocks, etc.

The stock market is up at least 8 straight sessions that I can think of off the top of my head.

I understand that the details of every deal will be different but I'm guessing that there are some guiding principles the most successful investors on this board use.