Sit down at the table and talk. 

Then using an amortization table I could estimate the current balance.  

Yeah..ok...And all teachers should have kids first...All doctors should have lots of medical issues before they can practice....All dentists should have lot of dental issues before they can practice...Every waiter should owner a restaurant before they can wait tables....Every car salesman should have bought multiple new cars before selling any....I get your point..... it would be great if every realtor had to have real life home ownership under their belt, so they have that BTDT experience..... but not gonna happen

Then buyer proceeded to leave $50k on the table without even realizing it.

I pay NO ONE "under the table".  

What experience are you bringing to the table?

If he's putting down 5% now and the terms are interest only, it's very likely he'll have to bring money to the closing table in 5 years to refi. 

Table 3 just now" Haha Great trip that would be!

He used DPA, and he essentially has a small 2nd mortgage covering the cash he couldn't bring to the table. 

So I understand I will have to come to the closing table on a refinance with about $68,000 + closing costs.