If you need an insurance agent who can look into it for you and provide you with some quotes, reach out. 

There are some public sources (www.city-data.com) that can provide good baseline information.

Private funding from a relative may provide flexible terms and reduced financial risk, but formal agreements are necessary, and interest paid is deductible for you but taxable for them.Traditional investment property loans offer stability and tax benefits like deductible interest and property taxes but require larger down payments.

You manage the headache of guests and communication, cleaning, etc. and he provides the property, but shares in the expenses and profits.

We're exploring creative ways to provide him with the cash needed for the down payment while avoiding triggering a taxable event.One strategy we're considering is purchasing his future primary residence ourselves, making the mortgage payments, and then, once we've built enough equity—comparable to the appraised value of his rental properties—transferring the title to him as a form of exchange.What are your thoughts on this approach?

Sometimes making a smaller profit and providing value is far better than holding out for a bigger payday on a bad deal, I like that.

Travel nurses are making bank and sometimes I think the locums companies provide lodging.

By putting the money into the house, however, it would provide some asset protection.

Only an investment team can provide the crucial local knowledge you need.Moreover, you'll need various resources to find, validate, inspect, renovate, and manage a property.

Advise him in writing that - email AND via US postal system with proof of delivery required that the lease remains in effect as is and that you, again, recommend that he file a claim with the provider of his renter's insurance for any losses he felt were sustained.