That was way more than I expected, but the plumbing and electrical ended up costing me several thousand dollars due to unforeseen problems with the existing service lines.  

There may be circumstances with your property that make accommodation, dog or no dog, financially prohibitive. 

@Chris Virgil-StoneGenerally the taxpayer who owns both the real estate asset being disposed and the replacement real estate asset must be the same.  1031 exchanges are easy to bust if you handle them the wrong way and don't have solid knowledge of the applicable code, regs, and case law.The questions you're asking are good and your thinking is on the right track, but they are advanced planning and structuring questions that are best directed to a tax professional you've engaged who can have the deep conversation with you and understand your facts, circumstances, and goals.

If you need financial assistance - because this is an unforeseen event - contact your city's Housing Department.

Under what circumstances would a taxpayer's rehabilitation tax credit not be limited?

How best to decide on major CapEx expenses (ie, vinyl windows that may last 20 years but are cheap vs aluminum that may last 50 but are expensive)How best to handle what happens if/when one of us wants out of this in the future for some unforeseen reason?

As someone whose parents passed i would feel unhappy if someone tried to lowball us due to the circumstances. 

Has anyone heard or done a buy and hold property through private lender and paid the debt off using the rent from the property, similar to a mortgage.Is this a very uncommon circumstance?

Often circumstances force us to do things that are not ideal.

But in the right circumstances there are a ton of possibilities within 1031.