Tons of entertaining space in the basement in addition to the 5th bedroom and full bath.

Additionally I am reading and researching 2 hours per day about real estate  rehab costs, plus other related topics. 

Robert Clement - Does your lease have late fees listed as additional rent?

If you chose to keep the contracting “at arm’s length” and avoid any future liabilities, then verify/hire your contractors and don’t bring them in-house and be clear about their roles and responsibilities beyond the Scope of Work.I think it’s also important to know for all of us here at BP that the word “contractor” carries a lot of weight and means very different things to different people, none of them incorrect.

In addition, as you have alluded to these are often illegal units which means they will not be worth anything on the resale.

Additional questions to ask?

If so, the additional accounting cost per LLC can be very, very low provided that you are doing the basic bookkeeping yourself and passing off to a CPA at tax time.

Do I go back with additional estimates and try to get the 20k difference off our handshake agreement?

@Manmohan Singh In addition to the other good advice you've received here be sure that:1. 

Referrals from fellow investors are worth their weight in gold and so Im asking on here.