Maybe I'm just cheap, or very rogue, but I say get a few professional masks, and go in and remove it ASAP.   

@Olivia DansereauIf this investor is the same LLC partner you mentioned in your post yesterday, then the transaction is a no-go for reasons of self-dealing with disqualified parties.The Solo 401(k) can lend withing the limits of state usury laws.Typically, a loan for real estate rehab would be 2-3 points and 12-16% interest.If the loan is including a "split of the profits" and an attempt to mask equity share of profits, then the IRS would likely challenge that as subject to UBIT taxation.

Thought I would add this scenario to the loop too.  

We seriously thought about buying a tiny house before we bought the duplex too!

This is low for the area, these units can easilly be $800 or $850 each.Current owner pays all water, sewage, and trash (that's going away ASAP).Roofs are original and show it, they need to go.Three HVACS are getting long in the tooth, one installed illegally. 

We originally decided that's what this was months ago, however I have been coughing and clearing my throat a lot lately this week even with a mask on as we cleared one last room and replaced all with pink batt....

The market could be much lower too. 

Walls and ceiling will be different colors so I will have some masking to do.

However this won't work because there are protruding ceramic soap dish and tooth brush holders hanging off the wall now, and I think a mirror at full length means it will be sandwiched between the wall and sink, it will most likely crack as I tighten and mount the sink against the wall...Plus it will be a big hassle to cut the holes underneath for the one drain, two supply lines and two sink mounting holes.

I don't have a lot picked out yet, though I see a number in the horse tooth area by the campground.