I wouldn't pay a deposit of any sort prior to looking at a car, house or motorbike. Why should an aircraft be different?
Sage advice! Having bought and sold a number of aircraft over the last 30 years, I wouldnt pay a nickel to anyone until I (or my representative) had physically examined the aircraft and done some basic due diligence. Any funds would then be escrowed until closing. There are a zillion R44's for sale so its not as though you will never find another one!
and then the whole balance - without having actually seen the aircraft!
Same here and I marvel at their willingness to do this! I'd stop short of calling it stupid, but sending a pile of money to a voice on the phone is a good way to be parted from your money. No need for it.