Is the extra headache really worth it? 

The lender has a duty to track their loans and recorded documents are notice of the change in ownership.The most serious problem is when a "kitchen table transaction" is used and not-recording the deed is used to intentionally hide the transfer. 

The records of the closed title company MIGHT show how they handled the issue, but more likely they missed this issue otherwise as part of their solution a mortgage satisfaction document would have been recorded at that time. 4.

True, but that doesn't mean the other people there aren't worth meeting. 

We had a couple "we buy ugly houses" type companies come in and offer less than even the lot itself is worth.

If you are only offering $100k I think its worth speaking to an agent and letting them make the $3-5k as an agent (if they would do it for that) on this deal. 

Working with a mortgage broker who specializes in investor programs can be helpful for better terms as conventional loan product lenders generally don't have the best DSCR terms.More info on DSCR loans: DSCR loans won't use your income to underwrite the loan.DSCR loans are based off of down payment, credit score and either actual or market rents so it helps to supercharge an investor's real estate goals and net worth.

Seller understands the house must go in order for the land to be worth anything).

Also calling the county and asking them who some use as consultants could be worth it.

Some insurance companies offer policies specifically designed for owner-occupied multifamily properties, so it’s worth asking about that option.The key is ensuring both your personal residence and the rental unit are adequately covered.