.• Retirement communities• Syndicates (from initial explorations, little transparency from providers, little oversight - almost leap of faith and trust in provider?)

I would find out who the manufacturer is and send it to them and confirm they will provide a warranty on this.

I also hold a couple of real estate forums in the area for people like yourselves to connect with service providers, GC's, etc. 

Don't depend on Aircover.Homeowners policy will not protect you if your renting as a STR.You need the correct STR policy to protect your property.

I specialize In helping investors like yourself locate, and secure investment properties and provide a hands off experience along the way.

My focus is on providing either turnkey-style space for those interested in temporary, infrequent use or long-term leasing for business folks who require conference room space (or perhaps event space).  

I wrote an article that I think you'd find value in that will provide some answers to your question: https://www.straightupchicagoinvestor.com/blog/6-must-knows

Mortgage recasting is a great option for homeowners who:Have received a windfall, such as a bonus, inheritance, or proceeds from selling another property.Want to lower their monthly payments without extending their loan term or going through the hassle of refinancing.Are satisfied with their current interest rate and loan terms.How to Get StartedIf you’re considering mortgage recasting, here are the steps to take:Contact Your Lender: Ask if they offer mortgage recasting and confirm your loan’s eligibility.Determine the Lump Sum Amount: Decide how much you can afford to put toward your principal.Calculate Potential Savings: Use an online mortgage calculator or consult with your lender to estimate your new monthly payment and total savings.Submit the Request: Once you’ve made the lump sum payment, your lender will process the recasting and provide a new payment schedule.Final ThoughtsMortgage recasting can be a powerful tool for homeowners looking to reduce their monthly payments and save on interest without the cost and complexity of refinancing.

Paying off the mortgage can provide peace of mind and simplify retirement, while keeping the debt allows you to leverage your funds for higher returns through investments.

Also, did they provide you those terms off the bat or after explaining your project?