The dilemma is the long term tenant's lease is not up until the end of the year, and I'm positive the roaches will not be rid of until the tenant is gone.  

Landlords must return security deposits with interest or give tenants written notice of damages being claimed within thirty days of when tenants move.

It wouldn't be the first time that a tenant put their landlord on notice about a safety problem one day, then the very next day they fall down hurt themselves (coincidentally of course!). 

A weeks notice is reasonable."

You could also simply give notice that at the end of their lease the rent will be increased by $1,000, which would probably have them move out anyway at the end of their lease.

In the summer and winter holiday season this town gets trampled with tourists from all over the world, so I am even more positive on its potential.

I noticed a lot post say I need a LOI, Lease and separate Option for the Seller.

It basically says "Notice: We have an uncontrollable cockroach infestation.

I'm diving into a potentially 100k+ rehab project in Central NJ (Bridgewater area) and would like to leverage some of your positive GC experiences to give this opportunity a high-percentage chance of success.

Thanks and positive vibes to all!