Buying tickets from a scalper. And I say:
Hate to ask but how would/will I know the tickets are real?
Are both okay?
I am not sure why I wouldn't use would, but I suggest:
I hate to ask, but how will I know the tickets are real?
I would ask "how do I know?"
If I were speaking direct to the ticket tout (BrE), I would say either:
How do I know the tickets are real?
Can you prove the tickets are real?
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.