Pre-Purchase Inspections - Tenant not co-operating

The owner has never seen inside Unit 2 and I need to get a plumber and electrician inside to check things before I sign a contract.  We are not using realtors.  This is an off market property.  Unit 1 and 3 were pretty rough.  Unit 2 could be a Taj Mahal but nobody knows.  When I came by w/ the plumber he said "could not check, they were eating dinner".  He did say he works a rotating shift.  I do believe he and his wife and 2 daughters live there.  The owner is very concerned about "upsetting the tenants" they have been there for 10 years and he has not raised rent and they are worried I will raise rent.  Also, the owner is foreign with broken English and difficult to communicate with and thinks i'm going to run his tenants / friends off.