Vacant properties in the winter run the risk of pipes bursting so avoid those.

You also have to deal with winter weather in the northern states and possibility of pipes freezing and higher heat costs (which would be paid by the tenant once rented out).

What are the best options i have to counter this?

The main "con" I've seen with trenchless sewer replacement options is that epoxy lining or pipe bursting methods will not solve a main sewer that has a 'belly' between the house and the city.

Protect yourself with knowledge about your counter-party whether it is a broker or lender and certainly shop the market to ensure your terms are fair and consistent with market trends.

We only got sunlight piped here twenty years ago. - Not taking into consideration the foundation issues.

However, in this case it’s worth circling back in 3 months, 6 months, or a year because this seller wants to sell, he’s just not ready to give up his fantasy deal.If the seller’s response is acceptance of the outline of my offer but countering on price or terms, it may be worth negotiating because we MAY be able to get to YES.My biggest profits have occurred when I made offers that were nowhere near what the seller was asking and yet WERE ACCEPTED, or with small modifications. 

The guy behind the counter added me into their database.

We put a lot of efford and attention into keeping basements dry, but we still have an occasional pipe burst or sump pump fail and see issues and when you get water in a basement; carpet can be dried and cleaned, it's the open cell pad that is holding on to gallons of water like a kitchen sponge.

Of course, you could also make the seemingly-reasonable counter-argument that you would have to have proof that you sent the letter, and how could you get that proof if the letter were to be forwarded (to an address not provided to you by the tenant) instead of being returned to you for you to use as evidence later that the last known address was a dead-end?