Indicates he will pay the balance in seven days. 

No offense but these are basic questions that indicate you haven't really educated yourself on the basics of managing rentals.

The fact they are complaining online might be an indication the property manager dealt with them properly so be sure to ask the manager for their side of the story.7.

As most people indicated it's not a question of private money vs mortgage is more of a question of what do you qualify for.

As recent as today Biden and administration has said there are going to be doing immediate financial actions, so all signs indicate this is going to be the most rapid roll-out of the most extensive sweeping changes of any exchange of Presidential powers in history. 

Rates are going up industry wide for rental properties.   4th quarter of 2020 they went up an average of 6% and indications are they will go up 5%-30% in 2021.  2022 we are expected to see the same increases.  

Did he indicate that it was  extensive?  

@Nathan GreenAs @Charles Seaman indicated there is no set formula here.In my mind, finding and securing a deal might be worth 5% to 10% of the equity.If one works off this 5% to 10% guideline and ASSUMING THE OPERATION WORK LOAD IS SPLIT EVENLY (more on that later), then your 1/3 cash into the deal entitles you to 33% of the equity - allocating 5% to 10% of the equity for finding the deal - adding this to your 33% split based on cash might indicate you should receive 38% to 43% of the deal.

One of the last articles I can find indicates 80% of trades are automated, see below, the article is from June 2019.

Grades are another indicator of responsibility and car insurance companies at least used to tie rates for young drivers to their GPA.But ultimately, you will likely be asking for their parents to cosign the lease and running and background and credit check on both the tenant and their cosigning parent.