I bought a number of properties with leases in place.

Leases are NOT negotiable, terminable by the new owner. The only exceptions are foreclosures, and even here, some states like NJ even prohibits that. Normally, the lease is assigned to you at the closing anyway, so you'll get the original leases.

If your question is whether you can see the leases at the time of offer, or prior to signing of the PS contract, then it is up to the descretion of the seller.

In any event, the seller must provide to you in wrting prior to the closing the monthly amounts due on the lease, amounts owed, amount of deposit, back rents if any, and acknowledged and signed by the tenant prior to closing. This way, you won't get into a situation where the tenant is 3 months behind at the time of closing, and later on, when he moves, wants the deposit back, you then look to the seller, who then tells you he "used the deposit" to cover the back rent.