We have had systems fail and need replacement as soon as 10-12 years, and others lasting 30 or more years. 

You could talk to her and ask her once she's caught up if paying half on the 1st and half on the 15th is easier for her, but they MUST be paid on time.This may sound harsh, but you said "She has 3 children, and he bailed." 

I'd think you'd need to list both addresses as the replacement property concurrent with the single APN.

There are people on this forum that have over 50K in debt per month which I know sound daunting, but they don't care because their income from their properties is $100k per month.  

@Michael Kazalas, personally this sounds like too many cooks in the kitchen, but also a very clear violation of SEC rules around material involvement.Granted, I don't know much about fractional ownership other than vacation rentals, which are limited to 8 owners, typically.  

The emails themselves make it sound like I am communicating off platform and taking business from them.

So, I would not be allowed to turn the property into a quadplex BUT could turn it into a duplex with two ADUs, one attached (the additional unit built downstairs) and one detached (the renovated and converted garage).Does this sound accurate to the community here?

I currently have 2 single family rentals but am looking to delve in to fix and flipping as a way to supplement or hopefully replace my W2 income. 

After the current tenants move out, I need to replace the carpet and pad. 

You are now 4% lower than what you are thinking and it sounds like you maybe 10% lower soon enough..