That will allow good analysis of sale price appreciation and rental history. 

Once these type investments develop a history, I can see a market similar to peer to peer lending where default rates become standardized and known.  

If we bite off people’s heads when they admit disaster, it suppresses legitimate issues with these techniques.Just for context there is a lot of history with the OP and some of us on here going back years (like the thread I linked to above from about a year ago and several others if you use the search function with his name) with him minimizing the risks of how he was structuring these transactions and some of us being cautionary, warning him that exactly what happened here could happen, which made him defensive and dismissive. 

Also, many tenants are younger and have limited credit history.

HELOCs are much tricker than a closed end second - they don't typically allow you to close in an LLC and they are full doc qualification, meaning your FICO, employment history, income, DTI etc all come into play.

Continue Funding my Mid west BRRRR clients like the land if we get history I provide 100% of purchase and 100% of rehab and there is no monthly payments really helps these guys / gals scale..

There's quite a bit of history with this property management company:1) They failed to notify me when the original tenant stopped paying rent in early 2023.

Solid employment history.  

What documents do they require, what credit scores do they allow, how do they verify previous rental history, etc.?

Your credit, investment history and bank statements will likely be evaluated and you'll need to personally guarantee the loan, but you can close under your LLC.