The partnership or business arrangement puts each of you in substantial risk, both legally and economically.

All gov can do, under loss mitigation laws, is give home owners extra time to scrap up some money and make some sort of arrangement to resume paying their loans.

Should the tenant arrange for it and pay for it?

A common structure is either a debt arrangement (where the investor loans the money and gets a fixed return) or an equity split (where they share in the profits).

(Note that this is the typical arrangement for Airbnb rentals and other temporary rental-type properties.)Rental property used on a transient basis is depreciated over a 39-year period, not over 27.5-years as is the case with longer-term residential rental property (LTR). 

A SFH could make sense as a house hack if you found one that has an in-law arrangement but otherwise I'd say 2-4 units is the way to go.If house hacking doesn't make sense for you & your family, you'll likely need 20-25% down for an investment loan to buy & hold a property you won't be living in.

If your goal is to grow your LLC, consider arranging all of your properties under an agreement with your LLC to manage them & take all of the legal steps to ensure that the structure is correct. this may involve creating LLCs in the state(s) your LTRs are in to own the property and your PM LLC managing those properties, so that you don't have a concentration of all of your portfolio in one entity.

Think uber/lyft driver contractor structure.But the call center staff who handle the important stuff like leasing, arranging repairs, etc. work overseas and likely do not have intimate knowledge of your rental area.That said, I’m not bashing this model.

There's a chance they will say no (because they showed you 6 properties and expect to be paid) in which case perhaps you can arrange for their managing broker to set you up with a different agent in the same brokerage and give the first agent a referral fee for their efforts/ for referring you.  

But the way you have arranged the owner financing, and build costs, followed by refinance…this is a repeatable model for you.