I know a guy who hit $600k in a month, but he also spent $80k that month in marketing.

I PM'ed the same to posters, now 8 months later to see their experience.

Also, install follow-up. 

In most places, a verbal rental agreement is month-to-month.

However, my concern is:  would my parents be committing fraud by getting a HELOC, and then turning their primary into a rental just a few months later? 

For the first 6 months I ran it as a AirBNB and after 6 months I converted it to a long term rental.

Given the last commenter's advice about waiting for someone with experience to chime in the first time, that someone has to take a risk... the issue is that there is a high likelihood it will be either a loan-to-own lender looking to obtain functioning properties or a scam.If it's true, they would have SO much business; whatever funds they have available, they would be empty in 1 month or less because that would be the best deal in town if it's true.

For the first 6 months I ran it as a Airbnb after that I converted it to a long term rental.

That increases my monthly cash flow and it boosts the value of the property to increase my equity.The downside is that it can take a lot of work, time, money, and patience. 

This means, in effect, that he has not paid his rent for this month, July 2024.How can this happen?