Closing on property with illegal tenant

[Leeor Shimron]

I am looking to buy a single family house for a fix and flip in Bergen County, NJ. The seller told us there is a tenant who has illegally been living in his basement for the last 12 months. The property is not zoned as a two family. Legally, how can I evict him and how long should I expect that to take? This is the only issue that preventing me from closing on the project. Is this issue a deal breaker?