you cannot win such a bet. there is no doubt in my mind that there are MANY planets out there that will support life, and a fair sized subset of those will be very earthlike...
Billions. They have to be rocky planets, otherwise it is unimportant whether they have a main sequence sun or any sun at all. But if you are seeking lifeforms of our level, complex animal/plant lifeforms, pickings are slim to none. Odds are there isn't another earthlike planet in this galaxy, nor in the visible universe out to 14 billion lightyears.