Buying item through Ebay and Paypal, with return offer

[JaxonAvery]

Good Day, someone had listed on gumtree a Boat I value at $40,000 (if in great condition)

they are selling for $15,000 but I am on gold coast and they are in WA.

the will not let me inspect and wont let me get a Mechanic to inspect,

But are offering to do through Ebay/Paypal as a protection and offered 5 days after purchase for me to refund.

Any tips on a solution as I do not feel comfortable giving $15,000 through Paypal to have to deal with this if it turns Sour.

Thank you