I have no idea what is the structural or the mechanical condition.

Think ,insulating, attaching furring to the interior for drywall, limited design parameterers, running ductwork, and mechanicals, asthetics, etc.

If he has a signed contract he can put a mechanics lien on the property.Cut ties with the partner and Contractor.

This means that lien holders will be paid from the proceeds of the sale, in order of priority (property tax liens are always in first position, then mortgages (in the time order they were recorded) and other judgments, mechanics liens, etc.  

Can someone explain the actual mechanics of a Double-Closing?

The guy I called said he would use a mechanical snake first then use the jetter

Just like if a contractor put a mechanic's lien on the property, they wouldn't have liability to a tenant of the property.

Just from the standpoint of someone's whose first career was mechanic- I'm shocked that impala has made it 10 years and likely will start giving you some spendy issues soon.

And it's very difficult for a platform to build wholesale trust that their system's vetting mechanism is good enough to trust with what constitutes most people's single largest financial decision.  

Many of the houses in Baltimore are older 1900-1920 stock, which means that there's always standard work that needs to be done mechanically/code wise.