Depending on your loan structure I'm not even sure you could legally offer a personal guarantee outside of the loan for that money without committing mortgage fraud, as anything that could hinder the ability of the primary lender to recover their principal is supposed to be declared during their diligence period, and any material changes up to the point of taking the loan are supposed to be disclosed as well.

Have a candid conversation about how he plans to handle representing both sides and ensure you’re protected with things like a solid inspection period and contingencies.

They also offer a free trial period.  

If they have to move out while the treatment takes place, then we abate the rent for that time period.

I've created bullet points, changed wording often, rearranged pictures periodically, adjusted prices (super low for my area).

Just make sure you to have an inspection period to review things more. 

I am considering constructing a modular home which should reduce the construction period to 4-6 months versus traditional home construction.

Very rarely do single family homes cash flow, at least not on a consistent basis over an extended period of time regardless of what your spreadsheet may suggest.

First, you'll lose a ton of money over that period.

This stabilization period is expected to be short-lived, creating a window for strategic investments.