We advertised it with a sign in the yard and it rented for our asking price within 10 days.

My lawyer made it clear that its risky signing the contract and waiting for the DOB to correct the issuel, back to that later. 

Do I need him to sign one after every closing or just once a year when preparing taxes?  

I'd post an open house on Craigslist and your Nextdoor communities, and put open house signs on and around the property.  

So just completed a home/termite inspection on a duplex, found termite residues (State of NC defines it as active termite infestation), there is minor noticeable damage on the shoe molding on the floor but no signs of wear and tear on the wall but I nor the inspector cannot tell without ripping apart the wall how bad the infestation is- the seller is willing to pay for a termite extermination but my concern is how much damage these termites have already done on the inside of my walls that I cannot see- is there a termite expert professional I can hire to inspect the home more in depth during my due diligence period or anyway for me to get a peace of mind for this matter? 

It's an extra step, but now it's a direct transaction, not a third-party transaction.

A few other strategies I've thought of are bandit signs, Every Door Direct Mail, and Facebook ads. 

If you wish to sign a new lease we can discuss options.Please let me know what your future plans are.You are welcome to call this home for as long as you like as you have been good tenants!

If they are signed on as "roommates" then do they have much fewer tenant rights on their side as opposed to renting out the top half as a unit? 

So they emailed me a contract extension, signed and sent back.