If you go with the partnership route1) You need to manage the money going in and out of the business bank account.2) File a partnership return and be responsible for issuing K-1's3) make distributions to you and your partner for cash flow that you receiveYou will likely spend many hours on a nice gesture.I may want to consider instead to give a christmas gift or a bonus for early completion of projects.

My underwriting would have this large negative cash flow for 7 years.I would do a thorough underwriting but want to show using quick math the issue so I will use the 50% rule.  

.: Quote from @Marcus Auerbach: A lot of buyers have a psychological issue with #3.

There's a good chance the issue(s) you face has already been discussed and answered.Ask questions in the appropriate forum.

Spoiler alert- Phx is quite a saturated STR area, and many STR's (although some are doing great) are having major occupancy issues. 

If there are any legal issues that I have to worry about etc. 

But it's rapid price growth and sales activity could indicate a more volatile market, with the potential for corrections if demand slows as affordability becomes an issue.

And will you have ongoing maintenance issues beyond your CapEx based on the building's age.I personally would be suspect of this deal.

Invoices go into the CC account the same as they would in the AP account and are attributed to the vendor who issues them.  

The other non-math issues I'm good handling myself.