Looking for advice re: inheriting an odd tenant lease agreement

[Angeline Kung]

I am considering to purchase an investment property that is tenant occupied. One of the tenants has an unusual lease agreement that is a 10-year rental lease with the rent locked in for 10 years and 6 months free rent upfront. The idea is that the seller wants to bring the rent up to market in a rent control area. Is this legal if the tenant signed the lease for a rent increase above the rent cap for the same unit? What are my options? Can I create a new lease agreement before COE? Can I talk to the tenant? Or is this a red flag and should I not consider this deal? Thank you for your help!